A specialized pollen-harvesting device in western palaearctic bees of the genus Megachile (Hymenoptera, Apoidea, Megachilidae)

Abstract

Females of the European leaf-cutter bee Megachile (Megachile) pilicrus Morawitz possess a conspicuous brush of stiff, yellowish-red bristles on the ventral side of the trochanter and femur of their hind legs. Observation of pollen-harvesting females in the field and microscope analysis of scopal pollen contents revealed that the hind leg brush is a specialized device for combing pollen from the inflorescences of thistles and knapweeds (Cardueae, Asteraceae), the exclusive pollen plants of M. pilicrus. Hind leg brushes serving the same purpose were found to be also present in several Megachile species belonging to the subgenus Neoeutricharaea, indicating convergent evolution in these two different Megachile lineages. Compared to all other species, the hind leg brush of M. (Neoeutricharaea) apicalis is distinctly less developed which is assumed to be associated with its polylectic habit.