See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/309558581 Systematics of the South American species of Cylindrostethus Mayr, 1865 (Hemiptera : Heteroptera : Gerridae), with a new species from Amazonian Brazil and Peru Article  in  Invertebrate Biology · October 2016 DOI: 10.1071/IS14059 CITATIONS 0 READS 347 3 authors: Some of the authors of this publication are also working on these related projects: Phylogeny of Cercopidae (Hemiptera: Cicadomorpha) based on morphological data. View project Carla Floriano University of São Paulo 15 PUBLICATIONS   33 CITATIONS    SEE PROFILE Andressa Paladini Universidade Federal de Santa Maria 32 PUBLICATIONS   101 CITATIONS    SEE PROFILE Rodney Ramiro Cavichioli Universidade Federal do Paraná 144 PUBLICATIONS   463 CITATIONS    SEE PROFILE All content following this page was uploaded by Andressa Paladini on 28 March 2018. 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BDepartamento de Ciências Biológicas, Universidade Estadual Paulista (UNESP), Assis, SP, Brazil. CDepartamento de Zoologia, Universidade Federal do Paraná (UFPR), Curitiba, PR, Brazil. DDepartamento de Biodiversidade e Ecologia, Pontifícia Universidade Católica of Rio Grande do Sul, Division of Biological Sciences, Porto Alegre, RS, Brazil. ECorresponding author. Email: carlla.floriano@gmail.com Abstract. Water striders (pond skaters) occur worldwide and are conspicuous in most aquatic environments, but the taxonomy ofmany groups remains unresolved. Here we revise the South American species of the Palaeo- and Neotropically distributed Cylindrostethus Mayr, 1865, a genus characterised by its long, cylindrical body and fast jumping- gliding locomotion. Using a cladistic analysis of morphological characters, we confirm the subdivision of Neotropical Cylindrostethus into two major groups. Nine species of Cylindrostethus are recognised from South America, one of which was recently discovered in Amazonian Brazil and Peru: C. bassleri Drake, 1952; C. bilobatus Kuitert, 1942; C. drakei, sp. nov.; C. hungerfordi Drake & Harris, 1934; C. linearis (Erichson, 1848); C. meloi Floriano & Cavichioli, 2013; C. palmaris Drake & Harris, 1934; C. podargus Drake, 1958; C. regulus (White, 1879). Two species are placed in synonymy: (C. podargus=C. stygius Drake, 1961, syn. nov.); (C. linearis =C. erythropus (Herrich-Schäffer, 1850), syn. nov.). A key to the nine species is provided, along with detailed descriptions and illustrations. Additional keywords: Cylindrostethinae, Neotropical, taxonomy, water striders. Received 27 November 2014, accepted 1 April 2016, published online 31 October 2016 Introduction The family Gerridae Leach, 1815 currently comprises 75 genera and over 700 species of true bugs commonly called water striders or pond skaters (Polhemus and Polhemus 2008). The family is classified in eight subfamilies: Charmatometrinae, Cylindrostethinae, Eotrechinae, Gerrinae, Halobatinae, Ptilomerinae, Rhagadotarsinae and Trepobatinae (Andersen 1975; Damgaard et al. 2005; Polhemus and Polhemus 2008). Cylindrostethinae includes three genera: Cylindrostethus Mayr, 1865 with 18 species from Neotropical, Oriental and Ethiopian regions (nine Neotropical, nine Palaeotropical) (Hungerford and Matsuda 1960); Potamobates Champion, 1898 with 19 species from the Neotropical region (Buzzetti 2006) from Peru to southern Mexico (Hungerford 1936; Polhemus and Polhemus 1995; Padilla-Gil and Damgaard 2011; Morales- Castaño et al. 2013); and Platygerris White, 1883 with three species occurring in Central America and northern South America (Hungerford and Matsuda 1960). According to Hungerford and Matsuda (1960), Cylindrostethinae is characterised by a short rostrum surpassing the prosternum; male proctiger usually with various degrees of asymmetry; apical margin of abdominal sternum VIII asymmetrical in species of Potamobates and Platygerris; meso- and metathoracic tarsal claws absent in all species occurring in the western hemisphere; antennomere IV short and curved distally; and apical margin of clypeus loosely connected with base of the labrum by a membranous region. Despite these apparent synapomorphies, a phylogenetic study combining morphological and molecular data (Damgaard 2008) did not support the monophyly of the subfamily. Within the genusCylindrostethus, species share the following features: body cylindrical and elongate, at least four times as long as wide; head strongly narrowed anteriorly and widened posteriorly; antennomere II longer than III; abdominal spiracles closer to the anterior margin of the segment; and male genitalia bilaterally symmetrical in South American species (Drake and Harris 1934; Kuitert 1942; Hungerford and Matsuda 1960). According to Hungerford and Matsuda (1960), Palaeotropical species of Cylindrostethus are characterised by the following features: proctiger rounded, with basolateral processes directed Journal compilation � CSIRO 2016 www.publish.csiro.au/journals/is CSIRO PUBLISHING Invertebrate Systematics, 2016, 30, 431–462 http://dx.doi.org/10.1071/IS14059 mailto:carlla.floriano@gmail.com posteriorly; meso- and metathoracic femora as long as the maximum length of body, except in C. productus (Spinola, 1840) and C. costalis Schmidt, 1915; hind legs longer than length of body; anterior margin of mesosternum less pronounced; and presence of tarsal claws in meso- and metathoracic legs. On the other hand, the Neotropical species are characterised by having: basolateral processes of proctiger directed anteriorly; meso- and metathoracic femora distinctly shorter than maximum length of body; legs almost as long as body; anterior margin of mesosternum more pronounced; and meso- and metathoracic legs lacking tarsal claws. To date, all known Neotropical species of Cylindrostethus are restricted to South America. Cylindrostethus palmaris has been found in all South American countries except Chile and Uruguay (Nieser 1970; Mazzucconi et al. 2008), whereas the remaining Neotropical species – C. bassleri Drake & Harris, 1952; C. bilobatus Kuitert, 1942; C. erythropus (Herrich- Schäffer, 1850); C. hungerfordi Drake & Harris, 1934; C. linearis (Erichasin, 1848); C. meloi Floriano & Cavichioli, 2013; C. podargus Drake, 1958; C. regulus (White, 1879); and C. stygius (Drake, 1961) – are known only from northern South America (Drake 1952; Nieser 1970; Moreira et al. 2011a, 2011b). The lack of a robust phylogenetic hypothesis for Cylindrostethus reflects its systematics. Andersen (1982) suggested that Cylindrostethus might not be monophyletic given that Palaeotropical species have tarsal claws on the meso- and metathoracic legs whereas the Neotropical species do not. Drake (1952) proposed two groups to accommodate the Neotropical species of Cylindrostethus. His Group 1 (C. bassleri, C. bilobatus, C. erythropus and C. linearis) is characterised by: a unicolorous mesonotum with longitudinal impressions; posterior margin of sternum VI deeply excavated in the middle; first genital segment broad, not tapering posteriorly, truncate apically; and upper lobe of second genital segment with a pair of long, divergent, prong-like processes at base, directed anterolaterally and downwards. Group 2 (C. hungerfordi, C. palmaris, C. regulus, C. podargus and C. stygius) is characterised by: the mesonotum with dark stripes on each side; the posterior margin of sternum VI with broad, rounded emargination in males; the first genital segment tapering towards the apex, then abruptly narrowed into an acute tip; and upper lobe of second genital segment expanded sideways at base, forming a small, plate-like structure. The only previous phylogenetic analysis of Cylindrostethus, conducted by Polhemus (1994), was based on morphological data and yielded two sister clades, each exclusively comprising either Neotropical or Palaeotropical representatives. However, the author adopted the ground-plan character approach such that the data matrix has the Neotropical species represented as a single terminal, i.e. Polhemus assumed monophyly of the Neotropical Cylindrostethus. According to Polhemus, the lineage including South American species is supported by two synapomorphies: the absence of claws in mesothoracic legs and the apex of the proctiger being elongate and acute. In order to test the monophyly of the Palaearctic and Neotropical lineages, it will be important to sample all species for a comprehensive character list. Ecological and biological data on species of Cylindrostethus are scarce. In Brazil, some authors observed a few species in streams, rivers and ponds (Moreira et al. 2011a), usually in shaded habitats (Nieser and Melo 1997). They can be found in association with macrophytes, floating litter banks and exposed roots (Pereira et al. 2007). Roback (1966), in his expedition to the Peruvian Amazon, reported the curious behaviour of specimens of C. erythropus that were on trunks near water bodies and which jumped in any direction when disturbed. All species belonging to Cylindrostethus have a conspicuous behaviour when moving on the water surface, characterised by a strong push with the meso- and metathoracic legs followed by a long glide alternating between jumps and glides along a straight line. Species of other genera in the family are not as efficient when sliding at great speed over the water (Polhemus 1994). Taxonomic studies of the South American species of Cylindrostethus are also scarce and are mostly represented by descriptions of new species. The main goals of this paper are: (1) to provide a revisionofCylindrostethuswith an identification key to all valid species; and (2) to present a phylogenetic hypothesis for the South American species of Cylindrostethus and to evaluate the species- groups proposed by Drake (1952). Materials and methods Specimens were borrowed from several Brazilian and international institutions, here listed in alphabetical order of the abbreviation: AMNH, American Museum of Natural History, New York, United States of America; BMNH, Natural History Museum, London, United Kingdom; DZRJ, Coleção Entomológica Prof. José Alfredo Pinheiro Dutra, Rio de Janeiro, Brazil; DZUP, Coleção Entomológica Padre Jesus Santiago Moure, Curitiba, Brazil; INPA, Coleção de Invertebrados do Instituto Nacional de Pesquisa da Amazônia, Manaus, Brazil; SEMC, Snow Entomological Collection, University of Kansas, Lawrence, United States of America; LACM, Natural History Museum of Los Angeles County, Los Angeles, United States of America; MPEG, Museu Paraense Emilio Goeldi, Belém, Brazil; UEMS, Coleção Entomológica da Universidade Estadual do Mato Grosso do Sul, Mundo Novo, Brazil; UPTC,Museo deHistoriaNatural LuisGonzaloAndrade, Tunja, Colombia; USNM, National Museum of Natural History, Smithsonian Institution, Washington D.C., United States of America; ZSMC, Zoologisches Staatssammlung, Munich, Germany. Label data are given inside quotation marks, with a reversed slash (\) and separating lines on the labels. Specimens were examined and illustrated using a Zeiss dissecting microscope (SV 6, Jena, Thuringia, Germany) and Leica MZ 12.5 (Wetzlar, Hesse, Germany) and camera lucida. Phallus sclerites were illustrated with a camera lucida connected to an optical microscope (Wild M20, Gais, Appenzell Ausserrhoden, Switzerland). Specimens were identified based on the examination of original descriptions, type specimens, photographs and keys provided by Drake and Harris (1934), Kuitert (1942) andMoreira et al. (2011a). Genitalia of males and 432 Invertebrate Systematics C. F. B. Floriano et al. females were detached, immersed in a solution of 10% potassium hydroxide and placed in a warm bath for ~15min. Dissected structures were then washed with water, warmed up in a solution of 3% hydrogen peroxide to clear structures and then washed in 50% alcohol to remove air bubbles. After examination, dissections were stored in vials with glycerin and attached to the same pin as the specimen. Type specimens were not dissected. In this paper, the visible abdominal sternites are considered to represent sternites II–VII because the first abdominal sternite is reduced in individuals of all subfamilies except Rhagadotarsinae (Hungerford and Matsuda 1960; Andersen 1982). Series of photographs were taken using a Leica camera attached to a dissecting microscope and combined into multi- focal images using the Syncroscopy Auto-Montage software (High Wycombe, Buckinghamshire, England). Subsequently, stacked images and drawings were edited in Adobe Photoshop and Adobe Illustrator. Scanning electron microscope (SEM) images were obtained at the Centro de Microscopia Eletrônica da Universidade Federal do Paraná. Distribution records were retrieved from the literature and data from labels on specimens. A data matrix (Table 1) of 34 morphological characters (23 external and 11 male/female genitalia; Table 2), including 29 binary and five multistate characters, was assembled using WinClada (Nixon 1999–2002). Non-applicable characters were coded as ‘–’ and missing data were coded as ‘?’. Parsimony analyses were performed using TNT software (Goloboff et al. 2008) with all characters treated as unordered using two character-weighting schemes: equal weights and implied weights (Goloboff 1993), choosing values of K from three to seven. Tree searches were run using the implicit enumeration option, an exhaustive search function that computes all possible trees when taxon sampling includes fewer than 24 terminals. Clade support was calculated using Bremer support (i.e. decay index; Bremer 1994) and 100 bootstrap pseudoreplicates implemented in TNT under an equal-weighting scheme. Only unambiguous characters were optimised on the resulting cladogram. We used morphological characters to partition the study specimens into distinct phenotypes, with the most useful characters being the length of the connexival spines and the proctiger, the shape of the basolateral processes of the proctiger, phallus, and phallic sclerite and colouration. After completing a preliminary phylogenetic analysis using these phenotypes, those that were sympatric with their sister lineage were considered to be distinct species. If a phenotype was allopatric with its sister lineage, we then looked at geographic variation to determine whether it would be better to consider it a geographic variant or a distinct species. Results and discussion The phylogenetic analysis performed in this study yielded one most parsimonious cladogram (Fig. 1) of 43 steps, CI = 97 and RI = 98. The genus Cylindrostethus is supported by four synapomorphies: the elongated body (character 10), the acute connexival spines (character 191), the symmetrical male genitalia (character 210) and the elongated phallus (character 301). The two groups proposed by Drake (1952) were recovered in this morphology-based phylogenetic analysis. Polhemus (1994) conducted a phylogenetic analysis of the Palaeotropical species of Cylindrostethus; however, he assumed that the Neotropical species were monophyletic, and treated them as a single terminal. The author concluded that Cylindrostethuswasdivided into two sister clades, represented by the Neotropical and Palaeotropical species, and the phylogenetic relationships were addressed only in the latter group. In order to make further progress into the systematics of Cylindrostethus, to test and corroborate the monophyly of the Palaearctic and Neotropical lineages, it is important to sample all the species including an adequate characters list. The topology obtained in this study corroborates Group 1 proposed by Drake (1952). This clade is supportedbyone synapomorphy, the presence of spinules on abdominal sternites (character 120), with low Bremer support (1). We suggest this clade to be named linearis-group, because C. linearis is the oldest described species in the group. Five species are included in linearis-group: C. bassleri, C. bilobatus, C. linearis, C. meloi and C. drakei, sp. nov. The first three species were placed in Group 1 by Drake (1952), and C. erytrhopus is herein considered to be synonymous with C. linearis; C. drakei, sp. nov. and C. meloi, the latter included in this group by Floriano and Cavichioli (2013), are within the linearis-group in this phylogenetic analysis. Table 1. Data matrix comprising 34 morphological characters for Cylindrostethus taxa and outgroups (–) not applicable; (?) missing; (bold) outgroup; (*) polymorphic character Taxa 0 1 2 3 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 P. sumaco 1 0 1 1 1 1 0 0 1 – 0 1 – – 1 – 1 1 0 0 1 1 1 ? ? ? ? ? ? 2 ? ? ? – P. horvathi 1 0 1 1 1 1 0 0 1 – 0 1 – – 1 – 1 1 0 0 1 0 1 ? ? ? ? ? ? 2 ? ? ? – C. bassleri 0 0 – 1 1 1 0 0 1 – 0 0 0 0 0 1 1 0 1 3 0 0 1 1 0 2 1 1 0 ? ? ? 1 1 C. bilobatus 0 0 1 1 1 1 1 0 1 – 0 0 0 1 1 – 1 0 1 3 0 0 1 1 0 3 1 1 1 ? ? ? 0 1 C. hungerfordi 0 0 0 0 0 0 0 1 0 0 1 1 – – 1 – 0 – 1 1 0 0 1 0 2 1 2 1 0 0 1 1 0 1 C. linearis 0 0 1 1 1 1 0 0 1 – 0 0 0 0 0 0 1 0 1 3 0 0 1 1 0 2 0 0 0 1 0 0 1 1 C. meloi 0 0 1 1 1 1 0 0 1 – 0 0 0 0 0 1 1 0 1 3 0 0 1 1 0 3 1 1 1 1 0 0 1 1 C. palmaris 0 0 0 0 0 0 0 1 0 1 1 * 1 – 1 – 0 – 1 2 0 0 1 0 1 1 2 1 0 1 0 0 0 0 C. podargus 0 1 1 1 1 1 0 0 1 – 0 * 1 – 1 – 0 – 1 2 0 0 0 0 1 0 2 1 2 1 0 0 0 1 C. regulus 0 0 0 0 0 0 0 1 0 1 1 1 – – 1 – 0 – 1 1 0 0 1 0 2 1 2 1 0 0 0 1 0 1 C. drakei 0 0 1 1 1 1 0 0 1 – 0 0 0 0 0 1 1 0 1 3 0 0 1 1 0 2 0 0 0 1 0 0 1 1 Systematics of Cylindrostethus Invertebrate Systematics 433 Table 2. Explanation of characters used in cladistics analysis Character States Statistics Notes 1. Body shape (0) Elongated and cylindrical (length superior 4� the width) (Figs 10–13); (1) not elongated and cylindrical (length inferior 4� the width). Length: 1 IC: 100 RI: 100 The elongated cylindrical body (Drake and Harris 1934; Hungerford and Matsuda 1960; Hungerford and Matsuda 1962; Polhemus 1994) is a synapomorphy for Cylindrostethus. 2. Antennomere IV, shape (0) Cylindrical (Fig. 6A, B); (1) flattened (Fig. 6C). Length: 1 CI: 100 RI: 100 The flat antennomere IV is an autapomorphic feature of C. podargus. Drake (1958) described the antennae in this group as ‘fairly stout’. In some specimens, it shows a median longitudinal groove. 3. Antennomere IV, orientation (0) Straight (Fig. 6B,C); (1) curved (Fig. 6A). Length: 1 CI: 100 RI: 100 Hungerford and Matsuda (1960) suggested that the posterior curve of antennomere IV could be a putative synapomorphy of Cylindrostethinae. However, some species of Cylindrostethus (C. hungerfordi, C. palmaris, C. podargus and C. regulus) have a straight antennomere. Members of the subfamily Ptilomerinae also have a curved antennomere IV, varying from slightly to strongly curved (Andersen 1982). The studied specimens of C. bassleri lack the antennomere IV, so it was not possible to code the character in this case. The straight antennomere IV is a synapomorphic feature of the regulus-group. 4. Vertex punctations (0) Present (Fig. 4D); (1) absent (Fig. 4C). Length: 1 CI: 100 RI: 100 All species in the regulus-group (exceptC. podargus) have small punctations on the vertex, a synapomorphic character of this group. In other species, punctations are absent in the apical portion of the vertex. 5. Clypeus, pilosity (0) Glabrous (Fig. 4B); (1) densely pilose (Fig. 4A). Length: 1 CI: 100 RI: 100 The glabrous clypeus is a synapomorphic character of the regulus-group (except C. podargus). In other species of Cylindrostethus the clypeus is covered with setae. 6. Eyes, size of spines (0) Robust/large (Fig. 4F); (1) minute (Fig. 4E). Length: 1 CI: 100 RI: 100 The spiny ventralmargin of eyes is a synapomorphy of the regulus-group. They are well visible when specimens are examined in lateral view. In other species of Cylindrostethus, these spines are inconspicuous, forming small elevations on the margin of the eyes. 7. Female, mesonotum, posterior region of dorsal margin (0) Not extended above the metanotum (Fig. 2G); (1) extended above the metanotum, forming a protuberance (Fig. 2F). Length: 1 CI: 100 RI: 100 The protuberant dorsal margin extending above the metanonum is only present in females of C. bilobatus. Kuitert (1942) used this character in female descriptions. 8. General colouration (0)Predominantlyblack (Figs10A, B, 12, 13); (1) predominantly yellow (Figs 10C–F, 11). Length: 1 CI: 100 RI: 100 Species of Cylindrostethus are generally yellow or black. The yellow colouration is a synapomorphy of the regulus-group (exceptC. podargus), itmay vary from lighter to darker yellow, but never black. 9. Apterous, mesonotum and metanotum, black stripes (0) Present (Figs 10C, D, 11); (1) absent (Figs 10A, B, 12, 13). Length: 1 CI: 100 RI: 100 The black stripes in the regulus-group (except C. podargus) is a synapomorphic character. This feature has previously been used by Drake and Harris (1934), Drake (1952) and Kuitert (1942). 10. Mesonotum, width of black (0) Narrow, 3� narrower than median yellow stripe (Fig. 11A, B); (1) as wide as central yellow stripe (Figs 10C, D, 11C, D). Length: 1 CI: 100 RI: 100 The narrow black stripes in the mesonotum (state 0) was observed in a single species,C. hungerfordi. In the description of this species, Drake and Harris (1934) used this character as a diagnostic feature. When the stripes are as wide as the median yellow stripe, they may exhibit slight variation in conspecific specimens. 11.Male, anterior regionof the metacetabulum (0) Without tuft of setae; (1) with tuft of setae (Fig. 2A). Length: 1 CI: 100 RI: 100 (continued next page ) 434 Invertebrate Systematics C. F. B. Floriano et al. Table 2. (continued ) Character States Statistics Notes 12. Abdomen, sternites, spinules (0) Present; (1) absent. Length: 1 CI: 100 RI: 100 The spinules on the abdominal sternites of males are synapomorphic to the Neotropical species of Cylindrostethus. Old World Cylindrostethus have spinules on both abdominal and thoracic sternites. The absence of spinules is considered plesiomorphic for the genus. According to Polhemus (1994), the spinules first evolved in the abdomen, and later in the meso- and metathoracic sternites; in the same contribution, the author indicated that the absence of spinules was a synapomorphy of the Neotropical species. However, severalNeotropical species have spinules on abdominal sternites, and this is a synapomorphic feature of the linearis-group. The spinules are also present inC. palmaris andC. podargus, but they are polymorphic in these species. 13. Abdomen, sternites, spinules, amount and distribution (0) Abundant and agglomerated; (1) sparse and scattered. Length: 1 CI: 100 IR: 100 The spinules on abdominal sternites may be sparsely distributed (as in C. palmaris and C. podargus) or numerous and clumped together (a synapomorphic feature of the linearis-group). 14. Abdomen, sternites, location of spinules (0) On the centro-posterior region; (1) on the posterior region. Length: 1 CI: 100 RI: 100 Abdominal spinules are numerous and agglomerated in the linearis-group, and are located on the posterior region of sternites (as in C. bilobatus); alternatively, they can be located on the central region (as in C. bassleri, C. linearis, C. meloi and C. drakei, sp. nov.). 15. Abdomen, sternites, central concavities (0) Present; (1) absent. Length: 1 CI: 100 RI: 100 Species in the linearis-group (except for C. bilobatus) have concavities in the posterior region of abdominal sternites, a synapomorphic feature of C. meloi (C. meloi (C. bassleri (C. linearis C. drakei, sp. nov.))). 16. Abdomen, sternites V–VII, location of concavities (0) Encompassing sternitesV–VII; (1) only on sternite VII. Length: 1 CI:100 RI: 100 The concavities on sternites V–VII are an autapomorphic feature ofC. linearis; inC. bassleri, C.meloi andC. drakei, sp. nov. the concavity is seen only in sternite VII. 17. Abdomen, sternite VII, emarginate at middle (0) Absent (margin rounded) (Fig. 8A–D); (1) present (emarginate at middle) (Fig. 8E–I). Length: 1 CI: 100 RI: 100 Drake (1952) observed a conspicuous notch in sternite VII, and used it as a character to differentiate species in Group 1 from species in Group 2. This median notch is also found in two outgroup taxa (Potamobates horvathi Esaki, 1926 and Potamobates sumaco Cognato, 1998). 18. Abdomen, sternite VII, shape of median notch (0) Strongly marked (Fig. 8E–I); (1) subtle. Length: 1 CI: 100 RI: 100 In the linearis-group, the median notch is strongly marked, whereas in P. sumaco and P. horvathi the median notch is much less conspicuous. 19. Abdomen, connexival spines, shape (0) Rounded; (1) acute (Figs 7, 8). Length: 1 CI: 100 RI: 100 The conspicuous connexival spines is a synapomorphy of Cylindrostethus. When present, the spines in species of Potamobates are not acute (Hungerford and Matsuda 1960; Polhemus and Polhemus 1995; Polhemus 1994). 20. Abdomen, connexival spines, length (0) Very short; (1) short, ~3/10 the length of tergite VIII (Fig. 7C, D); (2) intermediate, ~1/2 the length of tergiteVII (Fig. 7A,B); (3) long, 3/5 the length of tergite VIII (Fig. 7E–I). Length: 3 CI: 100 RI: 100 In Palaeotropical species, the connexival spines may be elongate (longer than the tergite VIII), and usually reach the apex of tergite VIII in Neotropical species. The progressive prolongation of the connexival spines is considered apomorphic (Polhemus 1994). These spines are long in the linearis-group, of intermediate length in C. palmaris and C. podargus and short in C. hungerfordi and C. regulus. (continued next page ) Systematics of Cylindrostethus Invertebrate Systematics 435 Table 2. (continued ) Character States Statistics Notes 21. Abdomen, genitalia, shape (0) Bilaterally symmetrical (Figs 7–9); (1) asymmetrical. Length: 1 CI: 100 RI: 100 The male genitalia is bilaterally symmetrical in the Neotropical species of Cylindrostethus, and asymmetrical inPalaeotropical species (Hungerford andMatsuda 1960; Hungerford andMatsuda 1962; Polhemus 1994). The bilaterally symmetrical proctiger is a plesiomorphic condition, and the asymmetry is a consequence the enlargement of the left basolateral process (Polhemus 1994). The genitalia in species of Potamobates exhibit asymmetric variations, like processes in the posterior margin of tergite VIII (Hungerford and Matsuda 1960; Polhemus & Polhemus 1994;). 22. Genitalia, orientation (0) Not rotated (Figs 7–9); (1) rotated. Length: 1 CI: 100 RI: 100 In Potamobates, the male genitalia is rotated counterclockwise, except in P. thomasi (Hungerford and Matsuda 1960; Polhemus 1994;). 23. Sternum VIII, shape of margins (0) Constricted centrally (Fig. 8A); (1) straight (Fig. 8B–I). Length: 1 IC: 100 IR: 100 The constricted sternum VIII is an autapomorphy of C. podargus; however, this feature may not be as conspicuous in some specimens; in such cases, the specimen needs to be slightly rotated to accurately observe the shape of the sternum. 24. Proctiger, length (0) Long, with short basolateral processes (Fig. 9A–D); (1) short, with long basolateral processes (Fig. 9E–G). Length: 1 CI: 100 RI: 100 Species in the linearis-group have a short proctiger with long basolateral processes, whereas species in the regulus-group have a long proctiger with short basolateral processes. 25. Basolateral processes, length in relation to width (0) Elongate (Figs 8E–I, 9E–G); (1) subequal (Figs 8A–B, 9A,B); (2) 2�wider than long (Figs 8C, D, 9C, D). Length: 2 CI: 100 RI: 100 In Cylindrostethus, the proctiger has lateral expansions that show great variation (Polhemus 1994). For instance, in species of the linearis-group, the basolateral processes are longer than wide, in C. palmaris and C. podargus are nearly as long as wide and inC. hungerfordi andC. regulus arewider than long. 26. Basolateral processes, shape (0) Rectangular (Figs 8A, 9A); (1) oval (Figs 8B–D, 9B–D); (2) cylindrical (Figs 8G–I, 9F, G); (3) triangular (Figs 8E, F, 9E). Length: 3 CI: 100 RI: 100 The cylindrical basolateral processes are a synapomorphic feature of (C. bassleri (C. linearis C. drakei, sp. nov.)).Cylindrostethus bilobatus and C. meloi have triangular basolateral processes, and only inC.podargus the process is rectangular. In the remaining species, the processes are oval. 27. Proctiger, distance between the apices of basolateral processes in relation to proctiger length (0) Longer thanproctiger (Figs 8H, I, 9F, G); (1) narrower than proctiger (Figs 8E–G, 9E); (2) very narrow (Figs 8A–D, 9A–D). Length: 2 CI: 100 RI: 100 The distance between the apices of basolateral processes apexgreater than the length of proctiger is a synapomorphic feature of C. linearis+C. drakei, sp. nov. InC. bassleri,C. bilobatus andC.meloi, the distance is nearly equivalent to proctiger length. In the remaining species, the apices of basolateral processes are closer to each other. 28. Basolateral process, length (0) Long, reaching the connexival spines (Fig. 8H, I); (1) short, not reaching the connexival spines (Fig. 8A–G). Length: 1 CI: 100 RI: 100 The elongated basolateral process (reaching the connexival spines) is a synapomorphy of C. linearis+C. drakei, sp. nov. 29. Basolateral processes, shape of the apex (0) Rounded (Figs 8B–D, G–I, 99B–D, F, G); (1) acute (Figs 8E, F, 9E); (2) truncate (Figs 8A, 9A). Length: 3 CI: 66 RI: 0 In C. meloi and C. bilobatus, the apex of basolateral processes is acute; in C. podargus, the apex is truncate, and in the remaining species, the apex is rounded. 30. Phallus, shape (0) Semicircular; (1) elongate. Length: 2 CI: 100 RI: 100 The elongate phallus was recovered as a synapomorphy of Cylindrostethus. 31. Phallic sclerite, shape (0) Semicircular (Fig. 2C); (1) distinctly expanded, apex emarginate medially (Fig. 2B). Length: 1 CI: 100 RI: 100 The emarginate apex is an autapomorphy of C. hungerfordi. (continued next page ) 436 Invertebrate Systematics C. F. B. Floriano et al. The clade (C. bilobatus (C. meloi (C. bassleri (C. linearis, C. drakei, sp. nov.)))) is supported by a single synapomorphy: sternites abdominal with spinules (character 120). The clade (C. meloi (C. bassleri (C. linearis, C. drakei, sp. nov.))) is supported by two synapomorphies: abdominal sternites with medial concavities (character 150), and subquadrangular tergite VIII (character 331). The clade (C. bassleri (C. linearis,C. drakei, sp. nov.)) is supported by a single synapomorphy: the cylindrical basolateral processes of proctiger (character 262). Cylindrostethus linearis +C. drakei, sp. nov. share two synapomorphies: the distance between the apices of basolateral processes is greater than the length of the proctiger (character 270), and the basolateral process reaches and overlaps the connexival spines (character 280). Group 2 sensu Drake (1952) was also recovered as monophyletic, but with low Bremer support (1). This clade is supported by a single synapomorphy: apex of sternite VII rounded in males (character 170). We suggest this clade to be named the regulus-group, because C. regulus is the oldest described species included in the group. It consists of (C. podargus (C. palmaris (C. hungerfordi, C. regulus))). The clade comprising C. hungerfordi+C. regulus is well supported Table 2. (continued ) Character States Statistics Notes 32. Phallus, apex of sclerite, length of the projections (0) ~2� longer than thewidth of its confluence area; (1) as long as the width of its confluence area. Length: 1 CI: 100 RI: 100 The apical projections in the phallic sclerite as long as the width of its confluence area are considered a synapomorphic feature of the clade C. hungerfordi+C. regulus. 33. Tergite VIII, shape (0) Elongate; (1) subquadrangular. Length: 1 CI: 100 RI: 100 The subquadrangular tergite VIII is a synapomorphy of (C. meloi (C. bassleri (C. linearis C. drakei, sp. nov.))). 34. Apex of tergite VIII, shape (0) Acute (Fig. 2E); (1) rounded (Fig. 2D). Length: 1 CI: 100 RI: 100 The acute apex of tergite VIII is an autapomorphy of C. palmaris. Potomobates sumaco Potomobates horvathi Cylindrostethus podargus Cylindrostethus palmaris Cylindrostethus hungerfordi Cylindrostethus regulus Cylindrostethus bilobatus Cylindrostethus meloi Cylindrostethus bassleri Cylindrostethus linearis Cylindrostethus drakei sp. nov. regulus group linearis group 2 23 1 01 17 0 64 3 0 0 0 0 100 01 1 4 5 6 8 9 11 4 1 0 1 0 98 1 192130 34 07 20 1 2 0 98 1 2530 4 32 10 0 1 31 1 7 1 1 44 1533 0 1 12 0 63 1 26 2 35 2 27 28 0 16 00 69 Fig. 1. Most parsimonious cladogram obtained with equally weighted characters. Relative Bremer support is indicated above each node. Bootstrap is indicated below each node. Systematics of Cylindrostethus Invertebrate Systematics 437 (Bremer = 4) by four synapomorphies: short connexival spines (201); the shape of the basolateral processes (wider than long) (252); semicircular phallus (300); and apical projection of sclerite as long as its confluence area (321). According to Polhemus (1994), Cylindrostethus species are similar in their external morphology, differing primarily in small details of the male and female genital and pregenital structures. Comparing South American species of Cylindrostethus with species of other genera of Cylindrostethinae (e.g. Platygerris and Potamobates), we can affirm that the former show less intra- and interspecific variation. However, even the small morphological variation of the South American Cylindrostethus clade allows us to define characters and to resolve its internal relationships. Taxonomy Cylindrostethus Mayr, 1865 Type species: Cylindrostethus productus (Spinola, 1840) (= Cylindrostethus fieberi Mayr, 1865) by monotypy. Cylindrostethus Fieber, 1861: 33.[(gen. nov.: nom. nud.; key to genus]. Mayr, 1865: 444. [redescription of genus, description of first species, C. fieberi=Gerris productus Spinola, 1840]. Drake & Harris, 1934: 218, 238–239 [redescription, key to species, illustration].Kuitert, 1942: 135 [redescription, key to species]; Drake, 1952: 3 (new species- groups). Hungerford & Matsuda, 1960: 224–227, 504–509 [redescription, illustration]. Hungerford & Matsuda, 1962: 83–84, 103-111 [taxonomic remarks]. Polhemus, 1994: 3–6, 26 -27 [redescription, key, illustration]; Aristizábal, 2002: 81 [key, illustration]. Hydrobates Erichson, 1848: 614 [gen. nov.; name preoccupied by Hydrobates Boie, 1822 in Aves]. When erecting Cylindrostethus, Fieber (1861) did not include any species. The International Code of Zoological Nomenclature (Article 12.2) states that nominal genera described before 1931 must include one or more available nominal species, which should be clearly stated in the description (ICZN 2000). For this reason, the name Cylindrostethus Fieber, 1861 was unavailable (nomen nudum) until Mayr (1865) described a new species in the genus,C. fieberi. Although the genus authorship is sometimes attributed to Fieber (1861), Mayr is the authority of Cylindrostethus, the publication date is 1865 and C. fieberi Mayr, 1865 is the type species by monotypy. The genus redescription below refers only to the South American species. Diagnosis Body cylindrical and elongate, six times as long as wide (Figs 10–13); maxillary and mandibular plates fused, rostrum short, not reaching the mesosternum (Figs 3A, 15); usually apterous (except for C. palmaris); meso- and metathoracic tarsal claws absent (Fig. 3A, B); connexival spines shorter than the length of tergite VIII (Fig. 7); proctiger bilaterally symmetrical, basolateral processes directed laterally or anteriorly (Figs 8, 9). Redescription Male and female: apterous except for C. palmaris. Body cylindrical and elongate (Figs 10–13). Head: with median length 2/3 shorter than transocular distance, in dorsal view; lateral margins of vertex diverging anteriorly and posteriorly, C-shaped; antennal tubercles projecting and divergent, in dorsal view; eyes oval and protuberant, 1–2� as large as interocular width (Fig. 14); antennae smaller than prothoracic legs; antennomere I longer than II and III combined; antennomere III approximately half as long as IV; clypeus rounded anteriorly, basal margin absent (Fig. 4A, B); mandibular and maxillary plates fused (Fig. 3A); rostrum short, not reaching the mesosternum (Figs 3A, 15), article III 1.4–2.5� longer than article IV. Thorax: pronotum 1/2–1/3 as long as head width, posterolateral margins oblique, posterior margin slightly curved; mesonotum at least 1.4� as long as pronotum and metanotum combined; posterior margin slightly notched; metanotum subequal or slightly longer than pronotum. Prothoracic femora more robust than meso- and metathoracic femora, bearing spines on anterodorsal region; femora subequal or slightly longer than tibiae, tarsomere II 1.8–3.2� longer than tarsomere I, subapical tarsal claws present. Mesothoracic legs longer than metathoracic legs, femora 1.5–1.8� smaller than body length; mesothoracic tarsi flattened, longer than pro- and metathoracic tarsi, tarsomere I ~3� longer than tarsomere II; meso- and metathoracic tarsal claws absent (Fig. 3B). Metathoracic femora 1.6� as long as tibia; tarsal claws absent (Fig. 3C). Abdomen: approximately as long as mesothoracic femora: lateral margins parallel, divergent or convergent; tergite I ovate or cordate, smaller than others; tergites II–IV rectangular, equal in size. Male: connexival spines subequal to or shorter than length of tergite VIII (Fig. 7); proctiger bilaterally symmetrical, length variable (0.9–2.2mm), apicalmargin acute, basolateral processes variable: short with rounded or truncate apex, or long with rounded or acute apex (Figs 8, 9); apex of pygophore rounded to nearly acute (Fig. 8). Female: connexival spines distinctly smaller than length of tergite VIII, gonocoxae with or without spines. Colouration: varying from black to yellow, with black antennae and antennal tubercles (Figs 10–13). Comments This genus is easily distinguished from the other genera of Cylindrostethinae in having: body cylindrical and elongate, six times as long as wide (Figs 10–13), whereas in Potamobates and Platygerris the body length is less than four times the width; antennomere II longer than III, whereas in Potamobates and Platygerris antennomere II is equal to or smaller than III; abdominal spiracles closer to the anterior margin of the segment, whereas in Potamobates and Platygerris spiracle is located on the middle portion; Cylindrostethus has the proctiger bilaterally symmetrical with basolateral processes directed laterally or anteriorly (Figs 8, 9), whereas Potamobates and Platygerris have the basolateral process of proctiger directed cephalad and assymetrical. 438 Invertebrate Systematics C. F. B. Floriano et al. Species included in Cylindrostethus Cylindrostethus bassleri Drake, 1952. Distribution: Peru (Amazonas) Cylindrostethus bilobatus Kuitert, 1942. Distribution: Bolivia (Beni), Brazil (Mato Grosso*) Cylindrostethus costalis Schmidt, 1915. Distribution: Indochina Cylindrostethus drakei, sp. nov. Distribution: Brazil (Amazonas, Pará, Rondônia), Peru (Loreto) Cylindrostethus hungerfordi Drake & Harris, 1934. Distribution: Bolivia, Brazil (Amapá*, Pará), Guyana (East Berbice), Suriname (Brokopondo, Sipaliwini) Cylindrostethus linearis (Erichson 1848). Distribution: Bolivia (Beni), Brazil (Amazonas, Pará, Roraima), Ecuador (Napo), Guyana, Peru (Loreto) Cylindrostethus malayensis Polhemus, 1994. Distribution: Malay Peninsula below the Isthmus of Kra, and northern Sumatra Cylindrostethus meloi Floriano & Cavichioli, 2013. Distribution: Brazil (Amazonas) Cylindrostethus palmaris Drake & Harris, 1934. Distribution: Argentina, Bolivia (Beni),Brazil (Amapá,Amazonas,Bahia,Maranhão,MatoGrosso, Mato Grosso do Sul, Minas Gerais, Pará, Rio de Janeiro, Rio Grande do Norte, Rondônia, Roraima, São Paulo), Colombia (Caquetá, Casanare, Meta, Putumayo, Vaupés) Ecuador (Napo), French Guyana (Cayenne), Guyana (Demerara-Mahaica, East Berbice-Corentyne, Marowijne), Suriname (Brokopondo,Marowijne, Para, Sipaliwini), Trinidad&Tobago (Diego Martín, San Juan-Laventille, Sangre Grande, Siparia, Tunapuna- Piarco), Venezuela (Amazonas, Aragua, Baritas, Monagas) Cylindrostethus persephone Kirkady, 1899. Distribution: (Celebes) Cylindrostethus podargus Drake, 1958. Distribution: Brazil* (Rondônia), Peru (Loreto) Cylindrostethus productus (Spinola, 1840). Distribution: Ceylon Cylindrostethus quadrivittatus Bergroth, 1916. Distribution: (West Africa) Cylindrostethus regulus (White, 1879). Distribution: Brazil (Amazonas, Pará*), Colombia* (Putumayo), Peru* (Loreto) Cylindrostethus samarinda Polhemus, 1994. Distribution: Borneo Cylindrostethus scrutator (Kirkaldy, 1899). Distribution: Malaysia Cylindrostethus sumatranus Lundblad, 1933. Distribution: Sumatra Cylindrostethus vittipes (Stal, 1870). Distribution: Philippines. * New records. Key to species of South American Cylindrostethus 1.Wings well developed (Fig. 10E, F) .......................................................... ...........................................C. palmaris Drake & Harris, 1934 (in part) Wings not developed (apterous) (Figs 10A–D, 11–13)............................2 2. Antennomere IV straight (Fig. 6B) or flat and broad (Fig. 6C); male: apex of sternite VII not emarginate at middle (Fig. 8A–D); basolateral processes of proctiger distinctly shorter than wide, directed laterally (Fig. 9A–D) ...........................................................................................3 Antennomere IV slightly curved (Fig. 6A); male: apex of VII sternite conspicuously excavated at middle (Fig. 8E–I); basolateral processes of proctiger 3� longer than wide, directed anteriorly (Fig. 9E–G)......6 3.Mostly yellow (Figs 10C–F, 11); anterior portion of metacetabula with a tuft of setae (Fig. 2A) ............................................................................4 Mostly black (Fig. 10A, B); anterior portion of metacetabula lacking a tuft of setae ...........................................................C. podargus Drake, 1958 4. Lateral black stripes of mesonotum 3� as narrow as central yellow stripe (Fig. 11A, B); male: base of phallic sclerite large and emarginate at middle (Fig. 2B)..........................C. hungerfordi Drake & Harris, 1934 Lateral black stripes of mesonotum approximately as wide as central yellow stripe (Figs 10C, D, 11C, D); male: base of phallic sclerite not enlarged at middle, round (not emarginate) (Fig. 2C) ..........................5 5. Body length >20 mm; prothoracic tibiae yellow with longitudinal black stripes; males: basolateral processes of proctiger 2� as wide as long (Fig. 9D); females: apex of tergite VIII rounded (Fig. 2D).................... ........................................................................C. regulus (White, 1879) Body length �20 mm; prothoracic tibiae black; males: basolateral processes of proctiger 1–1.4� as wide as long (Fig. 9B); females: apex of the tergite VIII acute (Fig. 2E) .................................................. .........................................................C. palmaris Drake & Harris, 1934 6. Females: posterior margin of mesonotum projected over metanotum (Fig. 2F); males: basolateral processes of proctiger small, not visible in dorsal view (Fig. 7E); posterior region of sternites V and VI with minute spinules .............................................C. bilobatus Kuitert, 1942 Females: apex of mesonotum with indistinct projection, not extended over metanotum (Fig. 2G); male: basolateral processes of proctiger long, visible in dorsal view (Fig. 7F–I); central region of sternites IV–VI with minute spinules..................................................................7 7.Male: distance between apices of basolateral processes equal or slightly smaller than median length of proctiger (Fig. 9E); apices of basolateral processes of proctiger not concealed by connexival spines in dorsal view (Figs 7F, G, 8F, G) ......................................................................8 Male: distance between apices of basolateral processes larger than 1.2� the median length of proctiger (Fig. 9F, G), apices of basolateral processes of proctiger concealed by connexival spines in dorsal view (Figs 7H, I, 8H, I) .................................................................................9 8.Male: basolateral processes of proctiger rounded apically (Figs 7G, 8G) . ..........................................................................C. bassleri Drake, 1952 Male: basolateral processes of proctiger acute apically (Figs 7F, 8F, 9E) ....................................................C. meloi Floriano & Cavichioli, 2013 9.Mostly brown; male: lateral margins of abdomen slightly divergent posteriorly, tergite VII 1.2� as wide as tergite II; sternite VI depressed at lateral margins; basolateral processes slightly curved (Fig. 9G), strongly convergent, anterior width ~3/10 of posterior width .........................................................................C. drakei, sp. nov. Mostlyblackorbrown;male: lateralmarginsof abdomenstronglydivergent posteriorly, tergite VII 1.3–1.5� as wide as tergite II; sternites IV–V and VII depressed at centre; basolateral processes not curved (Fig. 9F), not distinctly convergent, anterior width about half the posterior width ..........................................................C. linearis (Erichson, 1848) regulus-group Diagnosis Antennomere IV straight; ventral margin of eye with large spinules; abdominal sternites without spinules or with few; sternite VII not emarginated; connexival spines short; proctiger long with short basolateral processes. Cylindrostethus podargus Drake, 1958 Cylindrostethus podargus Drake, 1958: 110–111 [description]. Cylindrostethus stygius Drake, 1961: 65–66 [description], syn. nov. Material examined Data labels sent by email byDr ThomasHenry.Holotypemale (USNM): ‘San Alejandro R.[,] Loreto, Peru [,]VII 58 [,] F. Woytkowski (White label)’ ‘Cylindrostethus podargusDrake[,] <’. (Photo by Thomas Henry). Allotype male (USNM): ‘San Alejandro R.\ Loreto, Pery\ VII 58\ F. Woytkowki’ ‘CJDrake\ Coll. 1956’ ‘PubMed Allotype\ Cylindrostethus\ , podargus\ Drake’. Other material examined. One male (SEMC): ‘[PERU]\ Rio San Alejandro\ (Pampa Sacramento\ Dept. Loreto July 1958\ Woytkowski’; Systematics of Cylindrostethus Invertebrate Systematics 439 one female (SEMC): ‘[PERU]\ Rio San Alejandro\ (Bampa Sacramento\ Dept.Loreto July1958\Woytkowski’ ‘Locality:RiverSanAlejandro (Bampa Sacramento)\ Department of Loreto, Peru.\ Date: July 1958.\ Collector: Felix Woytkowski Note: the larger water striders were taken in the\ middle of the river San Alejandro, far from the shores\ in places of stronger current.’; one male and two females (MPEG): ‘Brasil Rondônia\ PortoVelho\Rio–Madeira \ 23-V-1984’ ‘Brasil Rondônia\ Marclo Zanuto’; One male (MPEG): ‘Brasil Rondônia\ Porto Velho\ Ig. Tabocal\ M.E. R. (Rio) Madeira\ 23-V-1984’ ‘Brasil Rondônia\ Marclo Zanuto’. Note on type material. Holotype in excellent state of preservation. Allotype with abdomen broken distal to the VIII segment. Diagnosis Pronotum with anteromedial yellow stripe (Figs. (A, B). Males: basolateral processes of proctiger short, subquadrangular (Fig. 9A), directed sideways, 1.2–1.5� wider than long. Redescription Apterous. Body length: < 17.3mm, , 18.8 mm; distance between mesoacetabula: < 2.2mm, , 2.3mm. Head: clypeus densely pilose (as in Fig. 4A); vertex not punctate (as in Fig. 4C); eyes 1.1–1.4� wider than interocular distance; ventral margin with inconspicuous spines (as in Fig. 4E); article III of rostrum covered with setae (Fig. 5C), 1.5–1.6� longer than article IV; antennomere I 1.9� longer than antennomeres II and III combined; antennomere III 2/5 the length of antennomere IV, antennomere IV straight and wide, ~4/5 of head width (Fig. 6C). Thorax: mesonotum 2� as long as pronotum and metanotum combined; anterodorsal region of prothoracic femora with fewer than 10 short spines; prothoracic tarsi slightly shorter than metathoracic tarsi; anterior area of metacetabula lacking tuft of setae. Male: lateral margins of abdomen slightly diverging (A) (B) (C) (D) (E ) (F ) (G) Fig. 2. (A) Cylindrostethus palmaris, detail of metanotum, ventral view; (B) C. hungerfordi (male), phallic sclerite, ventral view; (C) C. regulus (male), phallic sclerite, dorsal view; (D) C. regulus (female), genitalia, dorsal view (E) C. palmaris (female), genitalia, dorsal view (F) C. bilobatus (female), detail of mesonotum, lateral view; (G) C. linearis (female), detail of mesonotum, lateral view. 440 Invertebrate Systematics C. F. B. Floriano et al. towards posterior region in dorsal view, tergiteVII ~1.1� aswide as tergite II; sternites IV–VI lacking small spinules and concavities, sternites VII–VIII with few sparsely distributed spinules; tergite VII not depressed posteriorly; connexival spines 1/2 the length of tergite VIII (Fig. 7A); sternum VII not emarginate at middle (Fig. 8A); lateral margins of tergite VIII parallel, convergent anteriorly, apex subquandragular (Fig. 8A), slightly constricted in ventral view; apexof pygophore rounded in ventral view (Fig. 8A); proctiger 2� as long as tergite VIII in dorsal view (Fig. 7A); basolateral processes short, subquadrangular (Fig. 9A) directed sideways, 1.2–1.5� wider than long; phallus elongate, 2� longer than wide, sclerite basally bifid, branches 2� longer than the area of confluence. Female: posterior margin of mesonotum lacking large protuberances (Fig. 2G); tergite VIII elongate with a slightly rounded apex; gonocoxae with spines on posterior region; connexival spines 0.31mm in length. Colouration. Mostly black (Fig. 10A, B). Head: yellow dorsally, lighter between eyes; clypeus black; frons yellow (Fig. 14A); black ventrally; article I of rostrum light brown, article II dark brown, article III varying from brown to black (Fig. 15A). Thorax: pronotumwith yellow stripe on anteromedial region; femora and tibiae yellow; mesonotum and metanotum black, covered with golden pubescence, with black longitudinal stripe on each side;mesopleuron,mesosternum,metapleuron and metasternum black, pleurites covered with slightly golden pubescence, sternites covered with slightly silver pubescence; meso- and metathoracic acetabula yellow; femora yellow, 1/6 of apical portion black. Abdomen: tergites and pleurites covered with golden pubescence, sternites covered with silver pubescence; tergites, pleurites and sternites (I–VII) black, apex of pleurite VII yellow; connexiva yellow in females, black in males, connexival spines black in both sexes. Male: basal area of tergite VIII black, apical area yellow; sternites and pygophore black, posterior region sometimes brown; central area of proctiger yellow. Female: tergite VIII yellow at lateral margins, brown at anterocentral region; dorsal region of gonocoxa yellow; central area of proctiger yellow. Comments Cylindrostethus podargus is easily distinguished from the other SouthAmerican species by having: a black colouration (Fig. 10A, B); apical margin of sternite VII not emarginate at middle (Fig. 8A) and sternites IV–VI without spinules. Drake (1958) described C. podargus (Fig. 16E) and three years later described C. stygius, syn. nov. (Drake 1961) (Fig. 16D). Both species are similar and we did not find substantial characters to differentiate them based on the original descriptions. Drake (1961) commented on differences among C. stygius, C. hungerfordi, C. palmaris and C. regulus, but did not even mention the previously described C. podargus. Additionally, the type specimens designated in both papers are identical (i.e. type locality, date and collector) (Fig. 16F, G). In fact, in the introduction of his 1961 paper, Drake mentions that there were seven Neotropical species of Cylindrostethus. However, he had previously described C. podargus (Drake 1958) and therefore, at that time, there would have been eight valid species, not seven. According toDrake (1961), type specimenswere deposited at the USNM, but ThomasHenry (pers. comm.) has indicated that there are no such specimens in the collection. Marcela Monné photographed the female paratype of C. stygius deposited in (A) (C) (B) Fig. 3. Ultrastructure of head and thorax. (A) Cylindrostethus palmaris, head, lateral view; (B) C. linearis, mesothoracic tarsomere II, lateral view; (C) C. palmaris, lateral view, detail of posterior tarsomere. Scale bar, Fig. 8 = 500mm; Fig. 9 and Fig. 10 = 100mm. Systematics of Cylindrostethus Invertebrate Systematics 441 (A) (B) (C) (D) (E ) (F ) Fig. 4. Ultrastructure of the head. (A)Cylindrostethus linearis, dorsal view (B)C. hungerfordi, dorsal view; (C)C. linearis, dorsal view; (D)C. palmaris, dorsal view; (E)C. linearis, detail of eyemargin, lateral view; (F)C. palmaris, detail of eyemargin, lateral view. Scale bar, Figs 11, 12 = 500mm; Figs 13–16 = 100mm. 442 Invertebrate Systematics C. F. B. Floriano et al. the BMNH, and we confirmed that labels are identical to those in C. podargus Drake, 1958. Based on these findings, we consider C. stygius, syn. nov. as a junior synonym of C. podargus, considering that Drake likely described the same species twice from the same type series. Ecological notes The species is known from Peru (San Alejandro River). The specimens were netted in the swift flowing water, off the shore (Drake 1958). Cylindrostethus palmaris Drake & Harris, 1934 Cylindrostethus palmaris Drake & Harris, 1934: 219, 222 [description, key]. Drake & Harris, 1935: 3 [note]. Kuitert, 1942: 135, 136–137 [redescription, key]. Hynes, 1948: 343, 346 [note]; Kort-Gommers & Nieser, 1969: 78, 79 [note, illustration]. Nieser, 1970: 118–119, 135, 137 [redescription, illustration]. Aristizábal, 2002: 81–86 [redescription, key, illustration]. Moreira et al., 2011a: 270, 273, 274 [redescription, illustration, key]. Moreira et al., 2011b: 6 [checklist]. Material examined Paratype female (USNM). ‘PARATYPE\ Cylindrostethus\ palmaris\ D & H (Red label, manuscript)’ ‘Cylindrostethus\ palmaris D & H. (Beige label, manuscript)’ ‘Cadras\ Trinidad BW. I\ Aug 20–21 (Beige label, manuscript)’ ‘Paratype No\ 51106 (manuscript)\ U.S.N.M (Red label)’ ‘Aug. Busck\ Collector’. Other material examined. Nine males, eight females (LACM): ‘Imperatriz, on\ Belém, Brasilia road\ Maranhao, BRAZIL\ July, 1960\ D. L. Tiemann’; nine males, three females (LACM): ‘24 kil. E. Formoso,\ Go., Brazil\ May 21, 1956\ F. S. Truxal’ ‘MACHRIS BRAZILIAN\ EXPEDITION - 1956\ LOS ANGELES\ COUNTY MUSEUM’; one male (SEMC): ‘Brazil S.A\ 7–10 9–20–36’ ‘Vic. Joao Pessoa\ (SaoPhelipe)\River Jurua\ No. 375’; one male, one female (UEMS): ‘Brasil, MS, Tacuru\ Rio Iguatemi\ I-2009\ Floriano’; One male (DZRJ): ‘#42 Pleuston\ 15-V-2006\ UFRJ Pronex’; one male (INPA): ‘Brasil, AM, Manaus\ Rio Cuieiras 11\ 2.458650 lat\ 60. 34600 long’; eight males (LACM): ‘Jule 17, 1958, 42 km.\ SE. Maturis, Monagas\ Venezuela\ Arnold Menke’; one female (LACM): ‘July 3, 1958, 42 Kms.\ SE. Maturin, Monagas\ Venezuela\ Arnold Menke’; four males, one female (LACM): ‘June 16, 1958, 42 km.\ SE. Maturim, Monagas\ Venezuela\ Arnold Menke’; two males (USNM): ‘Trinidad B. W. I. Oct. 27–29 1938\ Carl J. Drake’; one female: ‘Ama-\zonas; Rio Mavaca\ Camp 65�060W2�2N, 150m. 16.27.89’ ‘Fhipps-FUDECI Exped.\ by American Museum\ of Natural History\ D. A. Grimaldi, coli.’; one male, one female (AMNH): ‘Berinitas\Dec42Venez\ P.Anduzee\Cylindrostethus\ palmaris\ Det. Drake’ ‘Donation from\ J. A. Slater\ Collection’; one male (USNM): ‘Venezuela Exp.\ Territ. Amazonas\ Upper Cunucunuma\ Julian May 27, 1950’ ‘J. Maldonado\ Caprilles Coll.’; three males (DZUP) ‘BR – AM Presidente\ Figueiredo\ Lago do Poraque\ 06–2011\ Floriano’; one male (DZUP): ‘BR-AM-Manaus\ R. (Reserva) Ducke\ Ig (Igarapé) Branquinho\ 07–2011\ Floriano’; one male (INPA): ‘BR 174–61 km de\ Manaus-AM\ 24–01–77\ B. Mascarenhas’ ‘C. palmaris - INPA)’ ‘Cylindrostethus palmaris\ D&H 1934\ det. R. Sampaio1980’; seven males, five females (INPA): ‘Brasil, AM, Manaus\ MAO, IG(Igarapé) Conj.\ Suframa IX 2003\ Sampaio’; two males, two females (AMNH): ‘GUYANA: Demerara District\ Yarowkkabre Creek on Linden\ Highway, June 16, 1986, K. &\ R. Schimidt & E. Traver, ex:\ narrow streamwith redwater\ moderate current, no riffle’; one female (AMNH): ‘Wismar,\ Brit. Guiana\ V. 9 1936\ Cylindrostethus\ palmaris’; one male (AMNH): ‘Georgetown, BrM\ II. 1922’ ‘Cylindrostethus\ palmaris\ C.J.D. D&H’; one female (INPA): ‘CEPLAC-estr. AM-10\ Km 30- Manaus-BR’ ‘18/VI/76\ Mario Dantas’ ‘Gerridae’ ‘Cylindrostethus palmaris - INPA’ ‘Cylindrostethus palmaris\ D&H, 1934\ det. R. Sampaio 1980’; four males, four females (INPA): ‘BRASIL: Mato Grosso\ Reserva Humboldt\ 10�110S 59�4800\ 75-VII- 1977\ Norman D. Penny’ ‘Cylindrostethus palmaris - INPA’ ‘Cylindrostethus palmaris\ D&H, 1934\ det. R. Sampaio 1980’; one male (INPA): ‘BRASIL: Amazonas\ Reserva Campinas\ 06/XI/1996\ Bento Mascarenhas’; three males (USNM): ‘Brazil.S.Amer.\ Rio Caraguata\ Matto Grosso [Mato Grosso do Sul]\ March 15, 1953\ F. Plaumann’ ‘<’ PubMed; ‘ J C Lutz\ Collection\ 1961’; one male, one female (AMNH): ‘Kobrene\ M. Grosso, 947\ J.C.M. Carbalho’; one male (INPA): ‘Rio Paru\ Pará\ J.C.M. Carvalho’; one female (MPGE): ‘Brasil Pará\ Cap. Poço\ Ig. (Igarapé) Braço\ Do Curral\ 22-IX-1987’; one male (MPEG): ‘Brasil Pará\ Irituia\ Ig.Sta.Grande\ 20/X/1987’ ‘Brasil Pará\ J.Dias’; one female (MPEG): ‘Brasil Pará\ S. Miguel do Guamá\ Ig. do Sete\ 19\X\1987’; two males, two females (MPEG): ‘Brasil Pará\ Serra Norte\ Serraria-Ig. (Igarapé) Azul\ 27. VI-1985’ ‘PubMed Brasil Pará\ R B Neto’; two males (MPEG): ‘Brasil Pará\ Serra Norte\ Salobo\ 04-VII-1984’; one female (MPEG): ‘Brasil Pará\ Serra Norte\ Est. Fofoca\ 07.V.1984’ ‘Brasil Pará\ M.F. Torres’; one female (MPEG): ‘Brasil Pará\ Serra Norte\ Caldeirão\ 21-VI-1985’ ‘Brasil Pará\ W. França’; two males, three females (MPEG): ‘Brasil Pará\ Serra Norte\ Rio Itacaiunas\ Caldeirão\ 21-VI-1985’ ‘Brasil Pará\ P. Tadeu’; five males, two females (MPEG): ‘Brasil Pará\ Serra Norte\ Pojuca\ II-VII-1984’ PubMed ‘Brasil Pará\ M. F. Torres’; one male (MPEG): ‘Brasil Mato Grosso\ Chap. (Chapada) Guimarães\ Faz. (Fazenda) Buriti.Coxipó\ 10-V-1984’ ‘Brasil Mato Grosso\ Marclo Zanuto’; three males, three females (MPEG): ‘Brasil Pará\ Serra Norte\ Serraria\ 27-VI-1985’ ‘Brasil Pará\ R. D. Thomaz’; one male (MPEG): ‘Brasil MT\ Chap. (Plateau) dos Guimarães\ Colégio Agr. Buriti\ 17-II-1986\ Col. I. S. Gorayeb’; one male (MPEG): ‘Brasil Mato Grosso\ Rod. AR 1 Vilhena Juína\ IG. (Igarapé)____ 3\16-V-1984’ ‘Brasil MatoGrosso’ ‘B.Mascarenhas’; onemale, one female (MPEG): ‘BrasilMato Grosso\ Chap. (Chapada) dos Guimarães\ Faz. Coxipó\ 10-V-1984’ ‘Brasil Mato Grosso\ Marclo Zanuto’; five males, two females (INPA): ‘Brasil: PA\ Sem. Pio X\ 11-VI-1975\ B. Mascarenhas’ ‘C. palmaris - Inpa’ ‘Cylindrostethus palmaris\ D&H, 1934\ det. R. Sampaio 1980’; one male, one female (AMNH): ‘BRASIL: PARA,\ Sta. Isabel\ B. Mascarenhas’ ‘I nov 1973\ Igarapé corrente\ na mata’; one male (MPEG): ‘Pará Carajás\ Est. Tres Alfa-\ 28.IV. 1983\ Tacainha km 5\ Macarenha and collegues’; two males, four females (SEMC): ‘British Guiana\ Supuruni Creek\ Aug. 1937\ S. Harris ‘(<)’ ‘PARAMORPHOTYPE\ Cylindrostethus\ palmaris\ L. Kuitert’; five males, six females (SEMC): ‘Bolivia S. A.\ R. Beni Cachuela\ Esperanza 9–37\ A. M. Olalla’ ‘PARAMORPHOTYPE\ Cylindrostethus\ palmaris\ L. Kuitert’; one female (SEMC): ‘Bolivia S. A.\ R. Beni Cachuela\ Esperanza 9–37\ A. M. Olalla’ ‘ALLOMORPHOTYPE\ Cylindrostethus\ palmaris\ L. Kuitert’. Notes on types. The paratype is poorly preserved: right antennomeres III–IV, left antennae, right mesothoracic leg and left mesothoracic tarsi are missing; the head is reattached (glued) to specimen. Diagnosis Polymorphic with respect to presence or absence of wings (Fig. 10C–F); male: basolateral processes of proctiger small, directed sideways, as wide as large, almost semicircular in shape (Fig. 9B). Female: apex of tergite VIII acute (Fig. 2E). Redescription Apterous or winged. Apterous form: body length < 17.5mm, , 18.9 mm; distance between mesoacetabula < 2.2mm, , 2.6mm. Head: clypeus glabrous (as in Fig. 4B); vertex punctate (Fig. 4D); eyes 1.5 to 2.1� as wide as interocular distance; ventral margin with conspicuous spines (Fig. 4F); rostrum: article III with sparsely distributed setae (as in Fig. 5A), 1.7–2.3� longer than article IV; antennomere I 1.3–1.6� longer than antennomeres II Systematics of Cylindrostethus Invertebrate Systematics 443 and III combined; antennomere III ~3/5 the lengthof antennomere IV, antennomere IV straight, 3/5 of head width (as in Fig. 6B). Thorax: mesonotum 1.3–1.5� longer than pronotum and metanotum combined; anterodorsal region of prothoracic femora often showing more than 15 short spines; prothoracic tarsi longer than metathoracic tarsi; anterior region of metacetabula with a tuft of setae (Fig. 2A). Male: lateral margins parallel or slightly convergent in dorsal view, tergite II 4/5–1� wider than tergite VII; sternites IV–VI lacking small spinules and central concavities; tergite VII not depressed on the posterior quarter; connexival spine 0.4–0.6 smaller in length than tergite VIII (Fig. 7B); sternites VII–VIII with or without a small number of spines; posterior margin not emarginate at middle (Fig. 8B); lateral margins of tergite VIII parallel or converging towards anterior and posterior regions, posterior margin rounded (Fig. 7B); apex of pygophore varying from rounded to nearly acute, in ventral view (Fig. 8B); proctiger 2� longer than tergite VIII, in dorsal view (Fig. 7B), basolateral processes short, directed sideways, as wide or wider than long, suboval (Fig. 9B); phallus elongate, ~2� as long as wide, sclerite bifid basally, branches 2� longer than area of confluence. Female: posterior margin of mesonotum lacking large protuberances on posterior region (Fig. 2G); tergite VIII elongated, apex slightly acute (Fig. 2E); posterior region of gonocoxae with spines; connexival spine varying 0.5–0.7mm in length. (A) (B) (C) Fig. 5. Ultrastructure of the rostrum, lateral view. (A)Cylindrostethus hungerfordi; (B) C. linearis; (C) C. podargus. Scale bar = 200mm. 444 Invertebrate Systematics C. F. B. Floriano et al. Colouration (apterous form). Mostly yellow (Fig. 10C, D). Head: in dorsal view, yellow, varying from entirely yellow to black at frons (Fig. 14B); yellow ventrally; articles I and II of rostrum yellow, 1/3 or 2/3 of the posterior region of article III black, anterior region yellow (Fig. 15B). Thorax: pronotum with median yellow spot; femora and basal portion of tibiae yellow; mesonotum and metanotum with black longitudinal stripes, wider than median yellow stripe; mesopleuron, mesosternum, metapleuron and metasternum yellow; mesothoracic and metathoracic acetabula with a laterodorsal brown spot; mesothoracic and metathoracic femora yellow, with black longitudinal stripe on dorsal and ventral region, inconspicuous in specimens of lighter colouration. Abdomen: covered with light brown pubescence; tergites (I–VII) black, sometimes with slightly marked median longitudinal yellow stripe; connexiva, pleurites and sternites (I–VII) yellow; pleurites sometimes showing black dorsolongitudinal stripe. Male: tergite VIII yellow, black at centroposterior region, or black at centroposterior region and at apex; sternite VIII yellow; pygophore yellow, or black apically; proctiger black, with basolateral processes and anterior region yellow. Female: tergite VIII yellow, black apically, or brown at central area; gonocoxae varying from yellow to brown, ventral region usually black; proctiger black, often yellow at margin and apex. Winged form. Body length:< 18.2mm,,19.3mm; distance between mesoacetabula of < 2.6mm, , 2.4mm. Head: eyes, in dorsal view, 1.8–2.0� wider than interocular distance; article III of rostrum 2.0–2.3� longer than article IV; antennomere I 1.3–1.5� longer than articles II and III combined. Thorax: male: lateral margins of abdomen convergent towards the posterior region in dorsal view, tergite II 0.7–0.8� wider than tergite VII; connexival spines 0.4–0.6� smaller than length of tergite VIII; basolateral processes 1.1–1.5� wider than long. Female: connexival spines 0.4–0.6mm in length. Colouration (winged form). Pronotum with yellow heart- shaped spot on anterior region, otherwise similar to apterous specimens (Fig. 10E, F). Comments Cylindrostethus palmaris differs from other Neotropical Cylindrostethus in possessing wing polymorphism (Fig. 10C–E). It superficially resembles C. hungerfordi and C. regulus, but differs in having basolateral processes of the proctiger with length subequal to width (in males) (Fig. 9D); phallus elongated, and branches of sclerite ~2� larger than its confluence area. It differs from C. hungerfordi in having black stripes on the mesonotum, more or less as large as median yellow stripe (Fig. 11A, B); the apical margin of phallic (A) (B) (C) Fig. 6. Ultrastructure of the IV antennomere, lateral view. (A) Cylindrostethus linearis; (B) C. palmaris; (C) C. podargus. Scale bar = 100mm. Systematics of Cylindrostethus Invertebrate Systematics 445 (A) (B) (C) (D) (E ) (F ) (G) (H ) (I ) Fig. 7. Male genitalia, dorsal view. (A) Cylindrostethus podargus; (B) C. palmaris; (C) C. hungerfordi; (D) C. regulus; (E) C. bilobatus; (F) C. meloi; (G) C. bassleri; (H) C. linearis; (I) C. drakei, sp. nov. Scale bar = 1mm. 446 Invertebrate Systematics C. F. B. Floriano et al. (A) (B) (C) (D) (E) (F) (G) (H) (I) Fig. 8. Male genitalia, ventral view. (A) Cylindrostethus podargus; (B) C. palmaris; (C) C. hungerfordi; (D) C. regulus; (E) C. bilobatus; (F) C. meloi; (G) C. bassleri; (H) C. linearis; (I) C. drakei, sp. nov. Scale bar = 1mm. Systematics of Cylindrostethus Invertebrate Systematics 447 sclerite is also not broad and emarginate (Fig. 2B). It differs fromC. regulus in the smaller body size; the anterior black tibiae, and tergite VII not depressed apically in males. Ecological notes This species is widely distributed, and can be found in rivers, streams and ponds. Some specimens were collected in the Iguatemi River (Mato Grosso do Sul State, Brazil), in shady areas of small forest stream with moderate flow. We collected it in deep parts of the forest stream and also near the margins. In the Branquinho Stream (Amazonas State, Brazil), specimens were in shallow areas with moderate flow and sandy substrate; the width between the stream margins was 1.5m. Specimens were also collected in a lake without riparian forest, but was shaded by concrete pipe. Hynes (1948) reported that C. palmaris specimens were collected in deep ponds and heavily shaded streams, where they are very agile. Cylindrostethus palmaris and C. regulus are sympatric in Jurua River (Amazonas states, Brazil). Cylindrostethus hungerfordi Drake & Harris, 1934 Cylindrostethus hungerfordi Drake & Harris, 1934: 221 [description]. Kuitert, 1942: 135–136 [key to species, taxonomicnotes].Nieser, 1970: 117, 137 [redescription, illustration]. Moreira et al., 2011b: 6 [checklist]. Material examined Holotype male (SEMC). ‘New Amsterdam, VII-1930, F.X. Willians\ Cylindrostethus hungerfordi Type D & H\ British Guiana S.A Near New Amsterdam. July 30 1923 F.X. Willians’. Paratype female (SEMC). ‘New Amsterdam, VII-1930, F.X. Willians\ Cylindrostethus hungerfordi Type D & H\ British Guiana S.A Near New Amsterdam. July 30 1923 F.X. Willians’. Other material examined. One male (INPA): ‘Serra do Navio\ (I.C.O. M.I)\ Amapá-II-961–4/61\ J.C.M. Carvalho col.’; four males (AMNH): ‘Guyana: Essequibo Prov;\ Little Takutu R. at main\ road from logging cmpnd\ Aug. 15, 1983K. Schmidt\ On deep & narrow, swift river - without rapids’; one male (AMNH): ‘FR. GUIANA [Suriname]: Lawa River shores\ opp. Anapaike Village, muddly\ riv. Str. w/ rot. Foliage\ 22. (A) (B) (C) (D) (E ) (F) (G) Fig. 9. Proctiger of males, dorsal view. (A) Cylindrostethus podargus; (B) C. palmaris; (C) C. hungerfordi; (D) C. regulus; (E) C. meloi; (F) C. linearis; (G) C. drakei, sp. nov. Scale bar = 0.5mm. 448 Invertebrate Systematics C. F. B. Floriano et al. (A) (B) (C) (D) (E ) (F ) Fig. 10. (A)Cylindrostethus podargus (male holotype) (image provided byMichele Touchet); (B)C. podargus (female); (C)C. palmaris (male, apterous form); (D) C. palmaris (female paratype, apterous form); (E) C. palmaris (male), winged form; (F) C. palmaris (female) winged form. Scale bar = 5mm. Systematics of Cylindrostethus Invertebrate Systematics 449 (A) (B) (C) (D) Fig. 11. Body, dorsal view. (A) Cylindrostethus hungerfordi (male holotype); (B) C. hungerfordi (female paratype) (image provided by Dra. Marcela Laura Monné Freire); (C) C. regulus (male); (D) C. regulus (female syntype). Scale bar = 5mm. 450 Invertebrate Systematics C. F. B. Floriano et al. XI.1963, B. Malkin’ ‘FRENCH GUIANA: Lawa river\ shores opposite Anapaike\ village, muddy river stream\ with much rotted foliage.\ Nov. 22, 1963\ B. Malkin’; one female (AMNH): ‘FR. GUIANA: Lawa River shores\ opp. Anapaike Village, muddly\ riv. Str. w/ rot. Foliage\ 22.XI.1963, B.Malkin’; one female (SEMC): ‘DutchGuiana\ VIII.19.1943\D.C.Geiskcs’ ‘With Mts, line\ 1 km 62e kamp\ Sanderesk’ ‘Cylindrostethus\ hungerfordi\ ORA\ det. Calabrese 1972’. Notes on types. The holotype is severely damaged; antennae, left metathoracic leg and left mesothoracic tarsus are absent. In the paratype, the left prothoracic legs and mesothoracic tibiae are missing. Diagnosis Pronotum with two black anterolateral spots; anterior region of prothoracic femora bearing more than 30 minute spines; mesonotum with narrow, longitudinal black stripes, 3� as narrow as yellow median stripe (Fig. 11A, B), basolateral processes short, directed sideways, ~2� as wide as long (Fig. 9C); apex of phallus sclerite long and emarginate at the middle (Fig. 2B). Redescription Uniformly apterous; body length: < 19.6mm, , 19.7 mm; distance between mesoacetabula: < 2.8mm, , 2.9mm. Head: clypeus glabrous (Fig. 4B); vertex punctate (as in Fig. 4D); eyes 1.8–1.9� as wide as interocular distance, ventral margin showing conspicuous spines (as in Fig. 4F); article III of rostrum 1.8–2� longer than IV, covered with small, sparsely distributed setae (Fig. 5A); antennomere I 1.5� longer than antennomere II and III combined; antennomere III ~3/5 the length of antennomere IV, antennomere IV straight, 7/10 of head width (as in Fig. 6B). Thorax: mesonotum 1.4� longer than pronotum and metanotum combined; anterodorsal region of prothoracic femora usually bearing more than 30 minute spines; prothoracic tarsi 1.6� as long as metathoracic tarsi; anterior region of metacetabula with a tuft of setae (as in Fig. 2A). Male: lateral margins of abdomen parallel or slightly convergent in dorsal view, tergite VII 0.9–1� as wide as tergite II; sternites IV–VI lacking spinules and concavities, tergite VII not depressed at posterior fourth; connexival spines 3/10� smaller than length of tergite VIII; sternite VII not emarginate at middle (Fig. 8C); lateral margins of tergite VIII converging towards basal and apical regions, apex rounded (Fig. 7C); apex of pygophore rounded in ventral view (Fig. 8C); proctiger ~2� as long as tergite VIII (Fig. 7C), basolateral processes short, directed sideways, 1.96–2.2� as wide as long (Fig. 9C); phallus slightly rounded, more or less as wide as long, branches of sclerite approximately as wide as its confluence area, apex of sclerite broad and emarginate medially (Fig. 2B). Female: posterior margin of mesonotum lacking large protuberances (Fig. 2G); tergite VIII elongate, apex slightly rounded; posterior region of gonocoxae bearing spines; connexival spines 0.4–0.5mm in length. Colouration. Mostly yellow (Fig. 11A, B). Head: yellow in dorsal view, lateroposterior region of clypeus black (Fig. 14C), yellow in ventral view; I, II and basal 2/3 of article III of rostrum yellow, others black (Fig. 15C). Thorax: pronotum dotted black on anterolateral region; femora and basal area of tibiae yellow; mesonotum with longitudinal black stripes 3� narrower than median yellow stripe; mesopleura and mesosternum yellow; metanotum black with longitudinal stripes 2� narrower than median yellow stripe, mesopleuron and metapleuron yellow; meso- and metathoracic acetabula with laterodorsal brown spot; meso- and metathoracic femora yellow, black longitudinal stripes ventrally and dorsally. Abdomen: covered with light brown pubescence; tergites I–VII with median longitudinal yellow stripe (as wide as lateral black stripes in males, and distinctly narrow in females); connexiva, pleurites and sternites I–VII yellow. Male: tergite and sternite VIII, pygophore and proctiger yellow, apex of tergite VIII black. Female: tergite VIII, proctiger and gonocoxae yellow, apex of tergite VIII black. Comments This species superficially resembles C. palmaris and C. regulus; however, it differs in having black stripes on the mesonotum, 3� narrower than the median yellow stripe (Fig. 11A, B). In males, the apical margin of the phallic sclerite is broad and emarginate (Fig. 2B). It is also much smaller than C. regulus; the tibiae lack black stripes, and the tergite VII is not depressed apically. It differs from C. palmaris in having the basolateral processes of the proctiger 2� as wide as long (Fig. 9C); the roundedphallus, and the sclerite branches of the phallus as long as the width of its confluence area. Cylindrostethus regulus White, 1879 Hydrobates regulus White, 1879a: 488 [description]; White, 1879b: 269 [taxonomic notes]. Cylindrostethus regulus Kirkaldy & Torre-Bueno, 1909 [nov. comb.]. Drake &Harris, 1930: 238 [redescription]. Drake &Harris, 1934: 219, 222–223, 238–239 [redescription, key, illustration]. Kuitert, 1942: 137 [taxonomic notes]. Moreira et al., 2011a: 270, 273, 274, 276. [redescription, key, illustration]. Moreira et al., 2011b: 6 [checklist]. Material examined The type series was photographed by Dr Marcela MONNÉ, and the photographs were examined in this study. Syntype, female (BMNH): ‘Hydrobates \ regulus B.W. \ TYPE’ (white label, handwritten) ‘Pres. by \ Perth Museum. \ B.M. 1953–629’ (white label, handwritten) ‘Labria \ R. Purus \ 10/9–74 \ Traill’ (white label, handwritten) ‘Hydrobates \ regulus’ (yellow label, handwritten) ‘SYN- \ TYPE’ (white label, outlined in light blue) ‘Type’ (white label, outlined in red) ‘BMNH \ #1005956’ (white label) ‘Hydrobates regulus B. W’ (white label, manuscript); syntype female (BMNH): ‘Hydrobates \ regulus B. W. \ Paratype.’ (white label) ‘Pres.by \ J. Ritchie \ Curator Perth Mus. \ B. M. 1929–79.’ (white label) ‘Labria \ R. Purus \ 16.9.74 \ Traill’ (yellow round label, handwritten) ‘Para-\ type’ (white label, outlined in yellow) [probably this label was placed by the museum curator posteriorly to the syntypes designation] ‘SYN- \ TYPE’ (white label, outlined in light blue) ‘BMNH (E) \ #1010360’ (white label). Other material examined. Two males, three females (SEMC): ‘Brazil S.A\ Jan - Apr. 1036\ A.M. Olalla\ No 1’ ‘R. (Rio) Amazonas (Nite)\ Region de\ Itacoatiara’; twomales, one female (SEMC): ‘Brazil S.A\ 9–25, 10–17–36 \ A.M. Olalla’ ‘Vle. Santo\ Antonio, River\ Eiru No. 3711’; three females (SEMC): ‘Brazil S. A\ 7–10 9–20–26\ A. M. Olalla’ ‘Vle. Joao Pessoa\ (São Phelipe) [Eurinepe]\ River Jurua\ No. 375’; two males, one female (UPTC): ‘Colombia, Putamayo\ Puerto Leguizano\ Caseiro\ Bajo Casacunte\ 00�04045.8–74�59043’9’ ‘178m (metros)\ 19–11–2008\ Jiménez (UPTC) col.’; two males, one female (INPA): ‘BR, AM, Coari, Urucu, Ig. (Igarapé)\ 05\486894–6541222’ 04-II-2006\ Couceiro col.’; one male, Systematics of Cylindrostethus Invertebrate Systematics 451 one female (AMNH): ‘PERU: Dept. (Departamento) Loreto:\ Rio Loreto Yacu,\ may 3, 1970, forest\ streem, B. Malkin’; one male (DZRJ): ‘2057’. Notes on types. Syntype lacking antennae and left mesothoracic tibiae and other syntypes lacking III–IV antennomere and left mesothoracic legs. White (1879a) did not designate types in his description of C. regulus, and based his description on a series of specimens, so all are syntypes. However, some specimens were wrongly labelled as paratypes, probably labelled by some museum curator posteriorly to the syntypes designation. Diagnosis Body length >20 mm; male: tergite VII depressed at posterior fourth; connexival spines 1/5 the medial length of tergite VIII (Fig. 7D). Redescription Uniformly apterous; body length: < 21.7mm, , 22.4 mm; distance between mesoacetabula: < 2.6mm, , 2.7mm. Head: clypeus glabrous (as in Fig. 4B); vertex punctate (as in Fig. 4D); eyes 1.6–1.9� wider than interocular distance in dorsal view, ventral margin with conspicuous spines (as in Fig. 4F); article III of rostrum with small, sparsely distributed setae (as in Fig. 5A), 2.0–2.5� longer than article IV; antennomere I 1.5� longer than antennomeres II and III combined; antennomere III 3/5 the length of antennomere IV, the latter straight, 3/5of head width (as in Fig. 6B). Thorax: wings not developed (apterous); mesonotum 1.3–1.6� longer than pronotum and metanotum combined; anterodorsal region of prothoracic femur with 5–18 small spines; prothoracic tarsi 1.2–1.4� longer than metathoracic tarsi; anterior region of metacetabula with a tuft of setae (as in Fig. 2A). Male: lateral margins of abdomen parallel or slightly diverging in dorsal view, tergite VII slightly wider than tergite II; sternites IV–VI lacking small spinules and concavities; tergite VII depressed posteriorly; connexival spines 1/5 the length of tergite VIII (Fig. 7D); posterior margin of sternite VII rounded (Fig. 8D); lateral margins of tergite VIII parallel, apical and basal area slightly convergent; apex truncate to subacute (Fig. 7D); apex of pygophore rounded to subacute in ventral view; proctiger long, ~2� longer than tergite VIII in dorsal view (Fig. 8D), basolateral processes short, directed sideways, 2.3–2.8� wider than long (Fig. 9D); phallus slightly rounded, more or less as wide as long, branches of sclerite approximately as wide as its confluence area (Fig. 2C). Female: posterior margin of mesonotum lacking large protuberances posteriorly (Fig. 2G); tergite VIII slender, apex rounded, gonocoxae lacking spines posteriorly (some specimens with a single spine); connexival spines 0.2–0.4mm in length. Colouration. Mostly yellow (Fig. 11C, D). Head: yellow in dorsal view (Fig. 14D); articles I and III of rostrum yellow, article III brown, sometimes lighter brown basally (Fig. 15D). Thorax: pronotum with black lateral stripes, wider than median yellow stripe; femora yellow; tibiae yellow with dark stripes medially, less conspicuous in darker specimens;mesonotumwith black stripe, slightly narrower than yellow median stripe; mesopleuron and mesosternum yellow; metasternum with black stripe, slightly wider or narrower than median yellow stripe; metapleuron and metasternum yellow; meso- and metathoracic acetabula dorsolateral brown; mesothoracic femora with black stripes ventrally and dorsally, posterior region with or without discreet stripes. Abdomen: covered with light brown pubescence; tergites (I–VII) black with narrow median yellow stripe; connexiva and sternites (I–VII) yellow to brown; dorsal region of pleurites (I–VII) with a brown longitudinal stripe. Male: tergite VIII with longitudinal brown median spot, or entirely brown at the middle; sternite VIII and pygophore yellow. Female: tergite VIII and proctiger with longitudinal median brown stripe at the middle; gonocoxae yellow, with or without ventral black stripe. Comments This species superficially resembles C. hungerfordi and C. palmaris. It differs from those by its larger body size, yellow prothoracic tibia with black stripes, and tergite VII apically depressed in males. It can be readily distinguished from C. hungerfordi by the width of the black mesonotum stripes, which are as wide as the median yellow stripe (Fig. 11C, D). Males of C. regulus differ from males of C. palmaris by the basolateral processes of the proctiger (twice as long) (Fig. 9D) and rounded phallus, with sclerite branches as long as the width of its confluence area. Examined specimens can be separated into two groups based on colour polymorphism and the variation in the shape of male genitalia. The first group includes yellow insects with a rounded pygophore in ventral view; tergite VIII rounded posteriorly; and apicalmargin of sternumVII rounded.The secondgroup includes mostly brown insects that are slightly larger, with the posterior margin of pygophore and tergite VIII nearly acute, and apical margin of sternum VII rectangular. In the redescription of this species, Drake and Harris (1930, 1934) described a variation of 18.50 to 20mm regarding the body size of the specimens. However, in this study all examined specimens have a body size larger than 20mm. linearis-group Diagnosis Antennomere IV curved; ventral margin of eyes with inconspicuous spinules; abdominal sternites with numerous and agglomerated spinules; sternite VII emarginate; connexival spines long; proctiger short with long basolateral processes. Cylindrostethus bilobatus Kuitert, 1942 Cylindrostethus bilobatus Kuitert, 1942: 137 [description]. Moreira et al., 2011b: 6. [checklist]. Floriano & Cavichioli, 2013: 191 [key, illustration]. Material examined Holotype male (SEMC). ‘Bolivia, S.A\ R. Beni Puerto\ Salinas 11–37\ A. M. Olalla (beige label)’ ‘< (yellow label) ‘HOLOTYPE\Cylindrostethus\ bilobata\ Det. L.C.Kuitert’; Allotype female (SEMC): ‘Bolivia, S.A\ R. Beni 452 Invertebrate Systematics C. F. B. Floriano et al. Puerto\ Salinas 11–37\ A. M. Olalla (beige label)’ ‘ALLOTYPE\ Cylindrostethus\ bilobata\ Det. L.C. Kuitert’. Notes on types. The holotype is in a good state of preservation, except for a hole in the mesopleura. The allotype is poorly preserved; antennomeres III–IV, right prothoracic tarsus and left mesothoracic tibiae are missing, and the tibiae and apex of the article IV of rostrum are damaged. Diagnosis Male basolateral processes elongate, projected forwards (Fig. 8E), not visible dorsally, apex acute, not reaching the connexival spines (Figs 7E, 8E); female with large processes on posterior margin of mesonotum (Fig. 2F). Redescription Uniformly apterous; body length: < 13.9mm, , 16.2 mm; distance between mesoacetabula: < 2.1mm, , 2.2mm. Head: clypeus densely pilose (as in Fig. 4A); vertex lacking punctations (as in Fig. 4C), eyes 1.3� as wide as interocular width in dorsal view; ventral margin showing inconspicuous spines (as in Fig. 4E); article III of rostrum 1.7� as long as article IV, setae covering 1/3 of anteroventral and dorsal region (as in Fig. 5B); antennomere I 1.6� as long as antennomere II and III combined; antennomere III half as long as antennomere IV; antennomere IV 3/5� as long as head width, slightly curved (as in Fig. 6A). Thorax: mesonotum 1.9–2.1� longer than pronotum and metanotum combined; anterodorsal region of prothoracic femora bearing fewer than 10 short spines; prothoracic tarsi slightly shorter than metathoracic tarsi; anterior region of metacetabula without a tuft of setae. Male: lateral margins of abdomen slightly divergent, towards posterior region, tergite VII 1.1� aswide as tergite II; sternitesV–VIbearing small spinules at posterior margins; tergite VII not depressed on posterior fourth; connexival spines 3/5 the length of tergite VIII; sternite VII bearing small, sparsely arranged spinules, lacking concavities, posterior margin conspicuously excavated at middle (Fig. 8E); lateral margins of basal III of tergite VIII slightly rounded, converging towards the anterior and posterior region, posterior margin slightly truncate (Fig. 7E); apex of pygophore rounded in ventral view (Fig. 8E); proctiger more or less equal in size to tergite VIII in dorsal view (Fig. 7E); basolateral processes elongate, directed forwards, apex acute, not visible in dorsal view (Fig. 7E), not reaching connexival spines (Fig. 8E). Female: posterior margin of mesonotum with large protuberances (Fig. 2F); apex of tergite VIII slightly rounded; posterior region of gonocoxae bearing spines; connexival spines 0.2mm in length. Colouration. Mostly brown (Fig. 12A, B). Head: yellow in dorsal view, frons brown, clypeus and vertex yellow (Fig. 14E); longitudinal dark brown stripe located medially, in ventral view; rostrum articles I and II yellow, article III black, gradually darkened towards the apex (Fig. 15E). Thorax: pronotum with median, light brown stripe; femora and basal III of tibia yellow; mesonotum and metanotum with brownish stripe; mesopleuron and metapleuron usually showing black dorsal stripe, brown in ventral view; mesosternum and metasternum yellow, covered with golden pubescence; meso- andmetathoracic femora yellow, gradually darkened towards apex. Abdomen: covered with golden pubescence; tergites, pleurites and sternites (I–VII) brown; connexiva yellow. Male: pygophore and proctiger brown. Female: lateral margin of tergite VIII slightly lighter that central area; gonocoxae brown, slightly darker dorsally; proctiger brown. Comments This species superficially resembles C. bassleri, C. linearis, C. meloi and C. drakei, sp. nov.; however, males of C. bilobatus differ in the shape of the basolateral processes of the proctiger, which are longer and concealed in dorsal view, not reaching the connexival spines (Fig. 8E). The females differ from other congeneric species in having a protuberant posteriormargin on the mesonotum (Fig. 2F). Cylindrostethus meloi Floriano & Cavichioli, 2013 Cylindrostethus bassleri, Moreira et al., 2011a: 272–273 [redescription, illustration] [misidentification]. Cylindrostethus meloi Floriano & Cavichioli, 2013: 187–192 [description, key, illustration]. Material examined Holotype male (INPA). ‘Brasil: Amazonas\ Ig. (Igarapé) Boiaçuzinho\ R. [Rio] Demeni - R. (Rio) Negro\ 5-X-1977. Dellone’ ‘C. erythropus – Inpa’. Paratype: three males, eight females (INPA): ‘Brasil: Amazonas\ Ig. [Igarapé]Boiaçuzinho\R. [Rio]Demeni -R. (Rio)Negro\ 5-X-1977.Dellone’ ‘C. erythropus – Inpa’; onemale, one female [DZUP], remaning specimens at (INPA). Othermaterial examined. One female, onemale (INPA): ‘BR [Brasil] – AM [Amazonas], Barcelos, Rio\ Acará\ 29-VII-2009\ PT 1006’. One male, four females (INPA): ‘BR [Brasil] - AM [Amazonas] R. [Rio Solimões Jutaí igarapé, afluente do rio\ Sapó’ ‘276119� – 6679997�\ 06-IX-2003\ N.Hamada & J. L. Nessimian’ ‘2062’; four males, eight females (INPA): ‘Brasil: Amazonas\ Ig. [Igarapé] Boiaçuzinho\ R. Demeni - R. (Rio) Negro\ 5-X- 1977. Dellone’ ‘C. erythropus - Inpa’; one female, one male (INPA): ‘BR [Brasil]–AM[Amazonas],Barcelos,Rio\Acará\ 29-VII-2009\PT1006’; one male (DZRJ): ‘BR - AM R. (Rio) Solimões J.\ Itaí ifarapé (Igarapé), afluente do rio\ Gapó’ ‘2276119 – 66799976 -\ IX-2003\ Hamada & Nessimian’ ‘2062’ PubMed. Diagnosis Mostly black (Figs 12C, D, 14F, 15F). Male proctiger with basolateral processes elongate, directed forwards (Fig. 9E), visible in dorsal view, apex acute, not reaching connexival spine (Figs 7F, 8F). Comments Cylindrostethus meloi closely resembles C. bilobatus, C. bassleri, C. linearis and C. drakei, sp. nov.; however, differs from the latter three species in having the basolateral process of the proctiger with an acute apex (Fig. 9E). It can be distinguished from C. bilobatus by the elongated basolateral processes of proctiger in males, which are visible in dorsal view (Fig. 7F). Females of C. meloi differ from those of C. bilobulatus in lacking large protuberances on the posterior region of themesonotum. This species was described by Floriano and Cavichioli (2013), but the authors did not specify the Systematics of Cylindrostethus Invertebrate Systematics 453 (A) (B) (C) (D) (E ) (F ) Fig.12. Body,dorsal view. (A)Cylindrostethusbilobatus (maleholotype); (B)C.bilobatus (femaleparatype); (C)C.meloi (maleholotype); (D)C.meloi (female paratype); (E) C. bassleri (male paratype); (F) C. bassleri (female paratype) (both at AMNH). Scale bar = 5mm. 454 Invertebrate Systematics C. F. B. Floriano et al. etymology. The specific epithet was given in honour of Dr Alan Lane Melo. Cylindrostethus bassleri Drake, 1952 Cylindrostethus bassleri Drake, 1952: 2–3 [description]; Floriano & Cavichioli, 2013: 191 [key, illustration]. Material examined Holotypemale (AMNH). ‘Rio Santiago,\ Peru IX – 4 – 24\ F6139’ ‘Bassler\ Collection\ AcC. 33591’ ‘-Holotype-\ Cylindrostethus\ bassleri\ < Drake’ ‘Holotype\ Cylindrostethus\ bassleri\ Drake’. Paratype male (AMNH). ‘Paratype\ by C. J. Drake\ Cylindrostethus\ bassleri\ (handwritten)’ (red label) ‘Rio Santiago\ Peru IX-4–24\ F 6134’ (beige label) ‘Cylindrostethus\ bassleri D&H’ (beige label)’ ‘H. Bassler\ Collection\ AcC. 33591’ (beige label). (Photos sent by Ruth Salas.) Paratype female (AMNH). ‘Allotype\ Cylindrostethus\ bassleri\ Drake’ (handwritten and red label) ‘Allotipe\ Cylindrostethus\ bassleri\ Drake’ (red label) ‘Rio Santiago\ Peru IX-2–24\ F 6124’ (beige label) ‘H. Bassler\ Collection\ AcC. 33591’ (beige label). Notes on types. The male paratype is damaged: antennomeres II–IV are absent. The left mesothoracic tarsus and right mesothoracic tibia are disassociated and glued separately on the label. The paratype female is lacking meso- and metathoracic legs. Diagnosis Males: basolateral processes elongate, projected forwards, visible in dorsal view; apex rounded, not concealed by connexival spines (Figs 7G, 8G). Redescription Uniformly apterous; body length: 16.9 mm; distance between mesoacetabula: < 2.3mm. Head: clypeus densely pilose (as in Fig. 4A); vertex lacking punctations (as in Fig. 4C); eyes 2� as wide as interocular width in dorsal view, ventral margin showing inconspicuous spines (as in Fig. 4E); article III of rostrum 1.7� longer than the IV, setae covering dorsal and 1/3 of anteroventral region (as in Fig. 5B). Thorax: mesonotum 2.1� longer than pronotum and metanotum combined; anterodorsal region of prothoracic femora bearing fewer than 10 short spines; prothoracic tarsi slightly shorter than metathoracic tarsi; anterior region of metacetabula without a tuft of setae. Male: lateral margins of abdomen slightly divergent, towards posterior region, tergite VII 1.1� as wide as tergite II; sternites V and VI bearing small spinules located centrally; tergite VII flat; connexival spines 0.9� the median length of tergite VIII; sternite VII lacking spinules, with slightly oblique concavities at sides, posterior margin conspicuously excavated at middle (Fig. 8G); lateral margins of basal III of tergite VIII slightly rounded, posterior region nearly parallel, posterior margin more or less truncate (Fig. 7G); apex of pygophore rounded in ventral view (Fig. 8G); proctiger subequal in length to tergite VIII, in dorsal view; basolateral processes elongated, directed forwards, apex rounded, visible in dorsal view, not reaching connexival spines (Figs 7G, 8G). Female: posterior margin of mesonotum lacking large protuberances (as in Fig. 2G); tergite VIII more or less quadrangular, apex slightly truncate; posterior region of gonocoxae lacking spines. Colouration. Mostly dark brown (Fig. 12E, F). Head: eye margin yellow in dorsal view, brown longitudinal stripe extending towards anterior region; frontoclypeus black (Fig. 14G), with longitudinal dark brown stripe medially, in ventral view; rostrum articles I and II yellow, III black, gradually darkened towards apex (Fig. 15G). Thorax: pronotum with median light brown stripe; femora yellow; tibiae black; mesonotum and metanotum with black stripe delimited by dark brown stripes, mesopleuron and metapleuron often showing dorsal brown stripe; mesosternum and metasternum brown, covered with silver pubescence; meso- and metathoracic acetabulum and femora yellow, gradually darkened towards apex. Abdomen: covered with sparse golden pubescence; tergites, pleurites and sternites I–VII brown; connexiva yellow. Male: tergite VIII brown; basal area of sternite VIII and pygophore yellow, apical area of sternite VIII and proctiger brown. Female: lateralmargin of tergite VIII lighter than central area; dorsal region of gonocoxae yellow, ventral region brown; brown proctiger. Comments This species closely resembles C. bilobatus,C. linearis,C. meloi andC. drakei, sp. nov. InC. bassleri, the basolateral processes of proctiger are elongated, but do not reach the connexival spines (Figs 7G, 8G), unlike C. linearis and C. drakei, sp. nov. It can be also distinguished from C. bilobatus and C. meloi in having the apices of the basolateral processes on proctiger rounded (Figs 7G, 8G). Cylindrostethus linearis (Erichson 1848) Hydrobates linearis Erichson, 1848: 614 [description]; Lethierry & Severin, 1896: 63 [catalogued]. Cylindrostethus linearis Kirkaldy, 1897: 258 [taxonomy]; Kirkaldy & Torre-Bueno, 1909: 210 [catalogue]. Schmidt, 1915: 362 [taxonomic notes]. Drake & Harris, 1930: 238 [redescription]. Drake & Harris, 1934: 220–221, 238-239 [redescribed, key, illustration]. Kuitert, 1942: 135–136 [key, taxonomic notes]. Nieser, 1970: 120–121, 135 –137 [redescribed, illustrated]. Moreira et al., 2011a: 270, 274 [redescription, illustration]. Moreira et al., 2011b: 6 [checklist]; Floriano & Cavichioli, 2013: 191 [key, illustration]. Hydrometra erythropusHerrich-Schäffer, 1850: 68–69, 923 [description, illustration], syn. nov. Hydrobates erythropus Lethierry & Severin, 1896: 63. Cylindrostethus erythropus; Kirkaldy & Torre-Bueno, 1909: 210 [catalogued]. Schimidt, 1915: 362 [taxonomic notes]. Drake & Harris, 1934: 219–220, 238–239 [described, illustration]. Kuitert, 1942: 135–136 [key, taxonomic notes]. Nieser, 1970: 119–120, 135–137 [redescription, illustration]. Aristizábal, 2002: 81, 86–87 [key, redescription, illustration]. Moreira et al., 2011a: 270, 273–274 [key, redescription, illustration]. Moreira et al., 2011b: 6 [listed]; Floriano & Cavichioli, 2013: 191 [key, illustration]. Material examined Pictures taken by Marcela Monné. Syntype male (BMNH): ‘Hydrobates\ linearis ed.\ Krit. Guy.\ Schomburgk (green label, manuscript)’ ‘Zool. Mus.\ Berlin (beige label)’ ‘3388 (brownish label)’ ‘SynTypus (red label)’; onemale syntype (BMNH): ‘Brit. Guyana\ Schomburgk\ N. 3388 (green label, manuscript)’ ‘Zool. Mus.\ Berlin (beige label)’ ‘Syn Typus (red label)’; one female syntype (BMNH): ‘Brit. Guyana\ Schomburgk\ N. 3388 (green label, manuscript)’ ‘Zool.Mus.\ Berlin (beige label)’ ‘3388 (brownish label)’ Systematics of Cylindrostethus Invertebrate Systematics 455 ‘Syn Typus (red label)’; one male syntype (BMNH): ‘H. linearis\ Typ\ Brit Guyana\ Schomburgk (beige label, manuscript)’ ‘Cylindrostethus\ linearis\ Erich (brown label,manuscript)’ ‘Zool.Mus\Berlin’ ‘Syn.Typus (red lab