Mouthpart dimorphism in male and female wasps of Vespula vulgaris and Vespula germanica (Vespidae, Hymenoptera)

Social wasps perform a variety of tasks with their mouthparts. Female workers use them to feed on carbohydrate-rich fluids, to build nests by collecting wood fibers and forming paper, to hunt and manipulate insect prey for feeding larvae as well as for brood care. Since male wasps neither feed on insects nor participate in nest building, sex-specific differences in mouthpart morphology are expected. Despite these different applications, general mouthpart morphology of male and female wasps from the genus Vespula was similar. However, males possessed significantly shorter mandibles with fewer teeth than females. Furthermore, the adductor muscles of the mandibles were distinctly smaller in males than in females. Male wasps showed a higher number of sensilla on the mandibles and the labial palpi. Mouthpart dimorphism and functional morphology of fluid uptake are discussed.