Effects of caffeine and various xanthines on hornets and bees.

The effect of caffeine was assessed on Vespa orientalis hornets maintained either in sealed breeding boxes or as entire colonies free to forage, and also on Apis mellifera bees within their hives. In a number of instances the hornets were also used to study the effect of various bodily extracts of queen hornets and of the following xanthines: Purine; hypoxanthine; uric acid; theophylline; and theobromine. The studied materials were found to exert an effect on three categories of activities: (1) Motor motility, flight, and construction; (2) sensory response to light (retinal and extraretinal), noise, irritability, orientation; and (3) physiological changes in appetite, copulation, oviposition, hibernation, resistance to cold, and longevity. Up to a point the produced effects were reversible. Throughout the period of experimentation the test insects did not show signs of tolerance or addiction towards caffeine.