The world will never look at the humble bush cricket the same way again, after research which appeared today in Biology Letters, a journal of Britain's Royal Society.
Stunned scientists reported today that the tuberous bushcricket (Platycleis affinis) has testes that amount to 13.8 % of its body mass. That's about the same as a man hauling around tyre-sized testicles weighing 5 kilograms each.
The cricket in question has the largest testes in relation to body weight of any known creature in the world.
"We couldn't believe the size of these organs. They seemed to fill the entire abdomen," said Karim Vahed, a behavioural ecologist at Britain's University of Derby.
The tuberous bushcricket beat all rivals in a testicular comparison of 21 species of bushcrickets, also known as katydids.
But for all its gonad grandstanding, the insect did not produce more sperm per ejaculate than others, and this offers an intriguing challenge to evolutionary theory.
Testes tend to be larger in species where females are more promiscuous. The assumption behind this is that the male which produces the most sperm has an advantage over his rivals in love.
But the tuberous bushcricket may cause this theory to be revisited, the authors say.
Its large reserves of sperm enable it to ejaculate, in tiny amounts, with a bigger number of females, thus boosting its chances of reproductive success.
"Traditionally it has been pretty safe to assume that when females are promiscuous, males use monstrously-sized testicles to deliver huge amounts of sperm to swamp the competition," said researcher James Gilbert of Cambridge University.
"Our study shows that we have to rethink this assumption. It looks as though the testes may be that big simply to allow males to mate repeatedly without their sperm reserves being exhausted."
"Extra large testes in bushcrickets allow males to transfer relatively small ejaculates to a greater number of females," Vahed says. "Males don't put all their eggs - or rather sperm - in one basket."