If you had to guess what creature in the world had the largest testes, I doubt you would guess that the prize belonged to a cricket.
The testes of the tuberous bush cricket (Platycleis affinis) are an internal affair, taking up most of the cricket’s abdomen. At nearly 14% of their body weight, they are disproportionately large when compared to other species. Just think, a 100kg human would be walking around with 14kg of testicles, which would be mighty uncomfortable.
Why do these crickets need all that sperm power? It is because their females are highly promiscuous. The male bush crickets do not release more sperm than normal in any given sexual act, but they can be called upon to do it so often they apparently need the reserves. In the world of insects, it is not worth missing an opportunity, and if the females are going to be all available like that, then a cricket needs some world-class balls.
But this is not the only sexual record held by crickets. An Australian species known as scaly crickets (Ornebius aperta) have the most frequent sex of any species in the world. These little guys can do it more than 50 times in a few hours, often with the same female!
Why do they have to keep this up? Because she eats it.
That’s right, cricket sex provides more than the spark for the next generation. Males actually produce a package called a spermatophore, which is sperm wrapped up in a nutritious protein package. When the males insert it into a special opening in the females, sometimes she just bends down to gobble up her yummy post-coital snack.
Australian spiny cricket males respond to this sabotage by releasing only a few sperm per package, between 5 and 225 sperm per copulation, an astonishingly low amount compared to the average (100,000). Yet when researchers measured sperm loads in females, they had up to 20,000 sperm stored away. This means that they had sex up to 200 times to collect that amount.
Of course the females were storing up more than sperm. They also gathered nutrients that will help them develop eggs for the next generation. Other species of crickets manage the situation by offering a courtship gift in the form of food from the dorsal glands that distract the female and give her something to eat during sex.
Some female crickets seek out males in order to get these tasty gifts. A study of 32 different species of bushcrickets showed that the larger the spermatophore, the more likely the females were to actively seek out males. These gifts are costly to produce, so species that produce small spermatophores may mate twice a night, while those with large spermatophores may mate only once or twice in a lifetime.
The final cricket sex record goes to the Mormon cricket, which produces a spermatophore that is 27% of its body weight. That’s a huge investment in wild oats, which is a good description, since most of the package is food. The Mormon crickets are flightless and form swarms similar to locusts. These great walking hordes are often so hungry that cannibalism is common.
Female Mormon crickets will compete for males just so they can get a feed, and the benefit for the male is that some of his sperm may make it to the next generation.
Crickets are not likely to be overly loyal to each other, because research on Spanish field crickets shows that individuals with more mating partners leave more offspring. This applies to both male and female crickets, so it is surprising that males will nevertheless protect a female that they have mated with.
Male crickets will linger near a female they have recently given their sperm to, not to scare away other suitors, but to protect the female from predators. He does this at his own peril, because males that hang about after sex are four times more likely to be eaten. On the other hand, the females are six times less likely to be eaten if he is there to protect her.
Male crickets are not confused about the goal of spermatophore transfer. But female crickets want more than just sperm from their partner. A meal (or several dozen meals) increases the male cricket’s chance of getting lucky.
Maybe they are not so different from people, after all.