Japanese scientists made this discovery accidentally, after one of them was bitten by one of these insects.
Shinji Sugiura, a biologist specializing in anti-predator strategies in animals at Kobe University, explained to AFP that, as a result of one of his students -Misaki Tsujii, co-author of the study, who appeared in the journal Current Biology- she was bitten by a male wasp, he decided to provoke a similar attack on himself.
Male wasps do not possess the dreaded venomous sting that females are equipped with. “Because I thought the males were harmless, I was surprised to feel the pain of a sting,” she said.
The hypothesis that certain male insects can sting with their genitals, the scientist explained, had been formulated before, but proof was lacking.
Sugiura suspected that the two large spines located on either side of the insect’s penis were responsible for the pain produced. To test his hypothesis in the lab, he offered wasps to two species of tree frogs.
“We observed many males that, at the moment of the attack, pierced the mouth or other organs of the frogs with their genitals,” he describes.
In one of the videos recording the test, one of the amphibians can be seen trying to chew the insect before removing it from its mouth with the help of a paw. In all, more than a third of the predators ended up spitting out the wasps after being stung.
Instead, when the experiment was reproduced with wasps that had had their genitals removed, the frogs gulped them down.
The difference between the two situations was “statistically significant, which suggests that it is a survival strategy in males that has influenced the evolutionary history of wasps,” stressed the researcher.
Beyond their reproductive role, the genital parts of insects have been little studied until now. And not for lack of interesting cases: for example, it has been discovered that sphinx butterflies use their genital organs to emit ultrasound against bats.
And Shinji Sugiura has investigated the way in which certain beetles manage to escape after being swallowed by exiting through the anus of their predators. Now, the biologist wants to determine if other families of wasps have the same genital defense system.