The secret sex life of plant bugs
Going by some of the horror stories in women's magazines, sex can be dangerous at the best of times. But a bit of whiplash or the odd carpet burn pales in comparison to the odious habits male plant bugs have developed.
Nikolai Tatarnic is a Canadian postgraduate student based at Sydney University's School of Biological Sciences. He became interested in the secret sex life of plant bugs, or Miridae, while studying evolutionary biology and sexual selection.
And his results revealed that for the female of the species, everything in the garden is far from rosy.
He has focused on the genus Coridromius, a group of tiny plant bugs only 2-4 millimetres in length. They can be found on scrubby waterside plants in Sydney, as well as in rain forests throughout Australia, the Pacific Islands, Asia and Africa.
Since the 1860s scientists have known that Coridromius males have dagger-shaped genitalia, but Nik was the first to suspect that this was because they practise a rough and ready form of mating known as traumatic insemination.
Sex between Coridromius bugs is remarkably unromantic. If girlfriends out there think they are getting a rough deal in the champagne and flowers department, listen to what these bug ladies have to put up with.
Is that a dagger in your pocket or are you just happy to see me?
Without any attempt at courtship the male pounces on the female, stabbing her in the side of the abdomen with his genitalia - a modus operandi that occurs in only a few other evolutionary distant insects such as bed bugs.
Nik describes his findings as, "extremely bizarre. It's like an evolutionary arms race where each sex tries to get the upper hand in controlling reproduction," he said.
"It seems that traumatic insemination has evolved as a means for males to take control of reproduction away from females," Nik explained. "By stabbing the female in the abdomen they circumvent female storage organs, female secretions, not to mention female behaviour aimed at deciding whether or not to use a male's sperm."
Coridromius plant bugs - males on the right, females on the left. Note dagger-shaped genitalia
But like their brainy human counterparts, the female Coridromius came up with a plan to deal with the cave man-like behaviour of the males. Over time, the females have evolved paragenitalia, a new set of reproductive organs, to counter the damage caused by the males.
In some species this has led to the appearance of a well-developed tunnel in the cuticle of the abdomen, leading to an internal sac which possibly digests the seminal fluids and maybe even the sperm.
Nik first attempted to confirm his theory by looking for holes in the abdomens of female plant bugs in collections, but to no avail. But after catching some local plant bugs and watching them mate, he noticed that the males had a favourite position - they were trying to penetrate the upper right side of the female's abdomen.
Going back to the lab, he realised that most of the bugs had been glued onto the paper on the right side of their bodies. After peeling the bugs off the paper, the tell-tale holes in their abdomens could easily be seen under a microscope.
Nik is also intrigued by the parallel development of traumatic insemination among organisms such as plant bugs and bed bugs that are thought to be far removed on the evolutionary tree. "We may have to consider the possibility that we have the evolutionary history completely wrong," he says.
