A number of bug and spider species engage in homosexual behavior, but researchers think it is simply out of carelessness.
"Insects and spiders mate quick and dirty," Dr. Inon Scharf of Tel Aviv University's Department of Zoology, said in a news release. "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 behavior has been shown to have evolutionary benefits in mammals and birds, such as providing practice for young adults and strengthening community bonds; but researchers have been scratching their heads over how the acts could help bugs.
Scientists have suggested it could help bugs "prepare for heterosexual courtship, dispose of old sperm, discourage predators, and distract competitors."
After looking at the behavior of 110 species of male insects, the researchers changed their mind. The team was not able to find a "clear" benefit to homosexual behavior in insects and arachnids.
For bugs and spiders, mating without the payoff of possible reproduction puts insects at risk for injury, disease and predation; it also wastes valuable energy.
The team found that bugs that experienced these disadvantages from mating had a life span that was about 25 percent shorter than those that did not.
Despite the consequences, about 85 percent of males in certain species engage in homosexual activities.
The team decided that the bugs didn't benefit from the behavior at all, but rather simply sometimes confuse males with females. About 80 percent of the observed homosexual behavior was a result of misidentification. In some cases, males that have recently mated with a female may carry her scent and confuse other prospective bachelors.
"The researchers say insects and spiders probably have not evolved to be more discriminating in their mating choices because the cost of rejecting an opportunity to mate with a female is greater than that of mistakenly mating with a male," the news release reported.
This is supported by the fact that insects and spiders have been known to mate with inanimate objects such as beer bottles.
"Homosexual behavior may be genomically linked to being more active, a better forager, or a better competitor," Dr. Scharf, 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."
