Homosexual Behavior in Insects the Result of Mistaken Identity, Study Suggests

The majority of homosexual behavior in bugs is most likely accidental, researchers from Tel Aviv University suggest in a new study published in the journal Behavioral Ecology and Sociobiology.

In birds and mammals, homsexual behavior is believed to offer evolutionary benefits by providing "practice" for young adults and maintaining alliances within groups. In the case of insects, researchers have previously speculated that such behavior could act as preparation for heterosexual courtship, a way to dispose of old sperm, distract competitors or discourage predators.

In reviewing research on 110 species of male insects and spiders, the researchers determined it may not be quite that complicated.

"Insects and spiders mate quick and dirty," Dr. Inon Scharf said. "The cost of taking the time to identify the gender of mates or the cost of hesitation appears to be greater than the cost of making some mistakes."

Homosexual mating is risky for insects and spiders, the researchers point out, requiring sperm, time and putting the creatures at risk for injury and disease. In all, the scientists determined that all of these factors shorten the lives of heterosexually active males by an average of 25 percent. Homosexual behavior, they estimate, is equally as costly.

Given this risk, as well as the fact that up to 85 percent of males in some species engage in homosexual behavior, the researchers argue that as much as 80 percent of cases of attempted same-gender mating is the result of belated or misidentification. Reasons for mistaken identity may be the result of some males and females resembling one another as well as some males carrying the scent of females they've recently mated with, the researchers posit.

According to the scientists, insects and spiders have not evolved to be more discriminating because the cost of rejecting an opportunity is greater than that of a failed attempt -- a theory supported by the fact that those species that exhibit homosexual behavior tend to display general sexual enthusiasm, mating with related species and inanimate objects, like beer bottles.

"Homosexual behavior may be genomically linked to being more active, a better forager, or a better competitor," Schart said. "So even though misidentifying mates isn't a desirable trait, it's part of a package of traits that leaves the insect better adapted overall."