Mating behavior of the eucalyptus longhorned borer (coleoptera: cerambycidae) and the adaptive significance of long "horns"

Sexual dimorphism in insect antennal structure is often attributed to differences between the sexes in sensitivity to pheromones, the antennae of one sex being more elaborately structured (for example, plumose). Males of the family Cerambycidae (order Coleoptera) often have longer antennae than females, but of a similar general structure, suggesting that selective factors other than sensitivity to pheromones are at work. Both sexes of the eucalyptus longhorned borer, a cerambycid, were attracted to eucalyptus logs that were larval hosts. There, males located females by antennal contact, and male mating success therefore depended on the walking rate and width of the antennal spread. Elongate antennae may benefit males by increasing antennal spread width, but have no such advantage for females, suggesting an evolutionary explanation for sexual dimorphism.