Effects of group size and starvation on survival of the Asian subterranean termite Coptotermes gestroi (Isoptera: Rhinotermitidae)

Abstract

Coptotermes gestroi forages on wooden structures and causes substantial damage in urban areas of Brazil. The survival of foragers may be influenced by either group size or caste composition. It was hypothesised that workers survive at higher rates in larger groups and consequently exhibit higher rates of food consumption and that soldiers represent a nutritional resource for foragers during starvation periods. To test the first hypothesis, groups of 100, 200 and 400 workers were placed in experimental arenas containing wood as food. After 28 days, the units were evaluated and the number of living termites and wood consumption were estimated and compared. An analysis of the data found that there were no significant differences within the group sizes on termite survival but that relative wood consumption was significantly higher in the smaller groups. To test the second hypothesis, groups containing workers and soldiers (9:1 ratio) or only workers were placed in experimental arenas with food present or absent. Survival for each caste was monitored at 3 day intervals over 9 days to estimate the cannibalism rate. Cannibalism was significantly higher in the starved groups, but the presence of soldiers did not influence the rate of cannibalism. Colony fragmentation and starvation are stressful conditions that lead foragers of C. gestroi to adaptive behaviours in order to enhance their survival.