Chemical communication in British social wasps (Hymenoptera: vespidae)

The alarm behaviour of VespuZa vulgavLs workers at the nest entrance, and of vulgar"is and gevmanioa workers at a foraging site, was studied. Four categories of alarm behaviour could be discerned: weak investigatory response (WIR), strong investigatory response (SIR), weak attack response (WAR) and strong attack response (SAR). Experiments showed that workers of Vesputa vulgavis possess an alarm pheromone which is located in the venom apparatus: one component, present in the venom sac, appears to release the stinging response, whilst another, possibly originating from the Dufour's gland, seems to have an attractant and alerting function. Worker heads contain an attractant. The stimuli involved in the precipitation of a stinging response include: sight of nest (and environs?), movement, colour, alarm pheromone and foreign odours. None of these can elicit an attack response in isolation. The presence of reproductives at the nest entrance appears to raise the threshold of the alarm response. Reproductives do not seem to exhibit alarm behaviour. Chemical analysis of the venom sac contents showed the probable presence of N-3-methylbutylacetamide and 4 spiroacetals. Ginger is an effective attractant, but only at sites where wasps are familiar with it. Sources of ginger are initially located chemotactically, but visual cues and taste are important on return journeys. Concentrated extracts are more attractive than raw ginger, but different fractions of the essential oil vary in their attractiveness, the most effective being those containing a large variety of sesquiterpenes. Although equally attracted to the most effective fraction, workers of vulgavis and to others. gevmani-oa differed in their response The saliva of vulgavis workers appears to contain an attractant serving to synchronize the removal of obstructions and possibly helping to co-ordinate nest building.