The researchers also found that beetles, through their homosexual encounters, transfer their semen to another male, and may in turn fertilise a female they may have never encountered.
While homosexual behaviour has long been seen in flour beetles, scientifically known as Tribolium castaneum, the new study is the first one to find the reason behind such a tendency.
We noticed that these male beetles spent quite a lot of time in this seemingly counterproductive behaviour and wondered what was going on, so we set up some experiments to find out, National Geographic quoted lead author Sara Lewis, an evolutionary ecologist at Tufts University in Medford, Massachusetts, as saying.
Organisms including insects, penguins, and primates, display homosexual behaviour, and researchers have laid out many hypotheses behind such tendencies.
While some have attributed the male behaviour as a need to practice breeding before meeting females, others claim that males need to get rid of old, less effective sperm before they encounter females.
In fact, there are some scientists who claim that homosexual behaviour is a method of exerting social dominance over other males.
To find out which hypothesis holds true, researchers marked individual males and females, then tracked their sexual exploits and simultaneously monitoring the paternity of any offspring born in the group.
They found that out of all the hypotheses, only one justified the homosexual behaviour among flour beetles-as males were dribbling sperm onto each other, it suggested that they might be getting rid of the old sperm and preparing the arsenal of fresh sperm for their next female encounter.
Also, the researchers 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.
The fact that a male could inseminate a female without directly breeding with her came as a big surprise.
Thus, one can say that the flour beetles' homosexual behaviour 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," said Lewis.
The findings of the study appear in the Journal of Evolutionary Biology.