Seed Beetles Are Locked in a Brutal 'Sexual Arms Race'

This is going to hurt. (Credit: Shutterstock) Cowpea seed beetle sex is complicated. During copulation, the male seed beetle, Callosobruchus maculatus, uses his sharp, spiky penis to damage females’ reproductive tract while depositing sperm. All the while, the female vigorously kicks at her suitor—it hurts! As studies have shown, males with longer, harmful penis spikes enjoy more reproductive success, to the detriment of their partner’s health. But the process of evolution has a way of balancing the scales. In a new study, Liam Dougherty of the University of Western Australia and colleagues closely monitored isolated populations of seed beetles in their lab, and they’ve concluded that males and females of this species are locked in a violent, multigenerational, “sexual arms race.” Sure, males wield destructive penises, but females, in turn, are adapting with their own defenses.