Such is the life of the Australian plague locust, a common pest that is targeted by the black digger wasp. The wasp is a parasite that creates living larders for her grubs. She stocks them with the bodies of paralysed insects. Last December, the locusts formed dense plagues in southeastern Australia just as the wasps were starting to collect fresh meat for their young. And Darrell Kemp from Macquarie University was watching as the two species collided.
Kemp found that mating locusts were far more likely to be targeted by the wasps than lone individuals. The pairs accounted for 3 percent of all the locusts in the area, but they made up 30 percent of the wasps’ targets. For lone locusts, the odds of being captured by a wasp were 1 in 200 for females and virtually zero for males. If they were having sex, those odds went up to 1 in 10. The risk was particularly poignant for the males. The wasps only ever stung the females but the males, unable to detach their penises, were “trapped in coitus” and “ultimately entombed alive”.
Several scientists have suggested that sex is a risky business for animals because they’re more conspicuous to predators and less likely (or able) to escape. However, there are few solid examples to back up this idea; Kemp’s study is one of them.
Reference: Kemp, D. (2011). Costly copulation in the wild: mating increases the risk of parasitoid-mediated death in swarming locusts Behavioral Ecology DOI: 10.1093/beheco/arr173