Olfactory evaluation of Andrena host nest suitability by kleptoparasitic Nomada bees (Hymenoptera: Apoidea)

Abstract

Kleptoparasitic Nomada bees (‘cuckoo bees’) are guided by olfactory cues in their local topographic orientation to Andrena host nests. Decisions regarding (1) the availability and suitability of a partly provisioned nest cell, (2) the threat of maternal host presence, and (3) prior visitation by another kleptoparasite, are all assessed olfactorily by the Nomada female while she is safely poised at the entrance to the host's ground nest. The influences of visual, tactile, acoustical and other sensory clues were controlled experimentally by presenting stimuli in artificial host nests. The nest approach behaviours of the kleptoparasites are comparable to non-parasitic bees. Although the host and parasite encounter the same odour cues for individual nest orientation, striking differences in their subsequent approach behaviours apparently result from the degree to which each generalizes the olfactory information available.