Social facilitation affecting tolerance to poisoning in termites (Insecta, Isoptera)

Summary: Previous works have shown that social interactions may enhance termite ability to overcome physiological stresses such as starvation and disease. We evaluated the effects of group size on termite tolerance to poisoning, by submitting groups of Cornitermes cumulans workers to an organophosphorus insecticide (chlorpyrifos). Survival of both, poisoned and non-poisoned termites, depended on the number of individuals in the group, presenting a peak at an density around 8 individuals/test tube. Survival of poisoned termites, however, showed a peak much lower than that of non- poisoned termites. We conclude, therefore, that socially induced ability to overcome physiological stresses in termites may be expressed even under "non-natural" stresses, such as poisoning by insecticides. The mechanisms leading to such a result remain to be investigated. It seems, however, that social facilitation may enhance (or trigger) biochemical and/or neurophysiological mechanisms that collaterally may help in the detoxification of insecticides in termites. In addition, we warn that laboratory experiments with termites/insecticides may be severely affected by the group size being tested.