Proceedings of the Royal Society B

A team of researchers has demonstrated the simultaneously unsurprising and highly disturbing fact that cutting various lengths off an insect's penis can make it more difficult to reproduce.

But the findings aren't as self-evident as they may seem, largely because the bug in question is so generously-endowed to begin with. The team from the universities of St Andrews and Bristol focused their attentions on Lygaeus simulans, a small bug just 11mm long, the males of which have penises almost two-thirds their body length and which is normally forced to drag its appendage beneath itself like a length of rope.


The bugs interested the team not just for its dimensions: the penis of the Lygaeus simulans is also devoid of nerves, muscles and blood vessels, and is apparently far longer than can capably be accommodated by the female bug.

The researchers wanted to know why the bug's penis was so long -- and as such what might happen if they were to make an... adjustment.

That's when they got out the scissors; in the study, published in Proceedings of the Royal Society B, biologists Liam Dougherty, Imran Rahman, Emily Burdfield-Steel, E. V. Greenway and David Shuker show how they snipped off varying lengths of the bug's penis, and then examined what happened when it attempted to mate.

Proceedings of the Royal Society B


The good news for the insects is that unlike almost every other species on the planet, the operation did not appear to bother them very much. Whereas most animals would experience serious medical problems, the bugs "copulated as normal" after the operation. However the team also found that the males were less successful in terms of offspring the more penis the team removed. A 5 percent shortened penis resulted in a large drop-off, while 30 percent also affected the rate of copulation.

The study also reveals how the team took micro-CT scans of the insects during copulation, and found that the insects relied on "coiling" the penis in order to inseminate the females. This procedure is that which was affected badly when the operation was performed. "We thus present rare, direct experimental evidence that an internal genital trait functions to increase reproductive success and show that, with appropriate staining, micro-CT is an excellent tool for investigating the functional morphology of insect genitalia during copulation," the team writes. By performing the operation they were able to reveal the unusual "experimental ablation" procedure performed by the male.

Human trials are not anticipated.