They found that homosexual encounters did not improve a male's sexual success with females, as measured by the number of offspring carrying his genes.
There was also no connection between homosexual activity and social dominance—male beetles that had many sexual encounters with other male beetles did not earn more attention from females.
What the team did find was that males were dribbling sperm onto each other. This suggested that males might be trying to get rid of old sperm, lining up fresher sperm for their next female encounter.
The team also found that if one male leaked semen on another male and the semen-covered male later bred with a female, the female's eggs could become fertilized with the sperm of the male she had never encountered.
That a male could inseminate a female without directly breeding with her came as a big surprise.
It reveals that the flour beetles' homosexual behavior yields a direct reproductive benefit, allowing males to inseminate females without expending time or energy having sex with them.
"We could not believe these results when we first saw them, so we ran the experiment over and over again to make sure it was actually happening," Lewis said.
A New Perspective
"This is excellent research," said entomologist Klaus Reinhardt at the University of Sheffield, U.K.
"So many papers look at these sorts of behaviors and immediately consider them from a human perspective. This paper has done a remarkable job of not sexing up the homosexuality and [instead] just asking why beetles do this."
Jane Brockmann is a behavioral ecologist at the University of Florida, Gainesville.
"Normally people would just write off this behavior, pitying the bugs as merely confused or overly sexed," she said.
"It is great to see it finally being explored objectively," she said.
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