Alkenes as a sexual pheromone in the alfalfa leaf-cutter bee Megachile rotundata

Abstract

Because of its special biological features, the leaf-cutter bee Megachile rotundata is particularly well suited for breeding and use as a pollinator for fodder plants such as alfalfa. Its mating behavior has been extensively studied. Behavioral tests have shown that males explore any black spot as a potential mating partner. However, exclusive selection of young virgin females suggests involvement of olfactory cues in addition to visual stimuli. Experiments demonstrated that mating behavior could be induced in males by lures covered with pentane extracts of the epicuticular waxes of young females. These extracts contain 35% fatty acids, 26% alkanes, and 39% monoenes. Variations in the monoene subfraction allow distinction between young virgin females, which possess more 7-pentacosene and 9-pentacosene, and older females, which have more 5-monoenes. The findings show that male mate-seeking and copulatory activity is stimulated only by young female monoenes. A 40% increase in this activity was observed.