Carpenter bees mate on-the-wing. Males grasp the females in flight and place their front or middle legs, which have fringes of long setae, over the compound eyes of their mate. It is thought that the dilated front legs of males of some species of carpenter bees collect and trap oils and odours that function during mating.Wittman, D. and B. Blochtein. (1995). “Why males of leafcutter bees hold the females’ antennae with their front legs during mating”. Apidologie 26, 181-195.
