Temperature dependence of the electrical resistivity of social wasp cuticle: a comparative study.

Resistance to electricity by social wasp cuticle is temperature dependent within the range of 1--40 degrees C. This was measured on the species Vespa orientalis (the Oriental hornet), Vespa crabro (the European hornet) and the wasp Dolichovespula saxonica. The resistance at first decreases with increased temperature, reaching a nadir which differs according to species, and then rises again up to 40 degrees C, the highest temperature tested. It is suggested that the cuticular changes in resistivity at different temperatures reflect the wasp's mechanism for detecting and regulating the temperature in their normal environment.

Theophylline induces diapause-like state in social wasps.

Feeding of theophylline to hornet workers from their moment of eclosion during the summer results in the following effects on the hornets: loss of appetite for proteins, inhibited ovarial development, no cell-building activity, negative phototaxis, gradual slow-down of spontaneous motor activity, difficulty in flight and orientation, and an overall behavior pattern reminiscent of hornet queens in nature when they are in a state of winter diapause. These findings suggest that theophylline exerts anti-juvenile-hormone-like effects on hornets and raise the possibility of utilizing theophylline baits to suppress pest hornet populations.