Sensilla numbers and antennal morphology of parasitic and non-parasitic bees (Hymenoptera : Apoidea)

The antennal forms and sensilla of 114 species of bees (Hymenoptera : Apoidea), representing all major lineages, were compared to ascertain the relationship between sensory structures and behavior. For all taxa, males and females of parasitic bee species do not differ significantly in the relative sizes of their antennal structures. For non-parasitic species, females have relatively longer scapes, but relatively shorter flagella. There are significant taxonomic effects in these relationships; the family Megachilidae is aberrant. These findings may relate to similarities in search behavior of males (both parasitic and non-parasitic) and parasitic females, which in general may be more dependent on longer-range olfactory cues, while non-parasitic females also use visual cues and contact or short-range olfactory cues. In the family Halictidae, there is a significant association between body-size and density of sensilla placodea. Among non-parasitic female bees, pollen specialists and generalists do not differ in the relative density of sensilla. Parasitic forms in Halictidae, however, have fewer sensilla placodea per unit aarea than do their hosts.