Male Crickets Bribe Their Mates With 'Gummy Bears'

David Funk
David Funk / David Funk

Everybody likes getting presents. It’s this fact that makes gift-giving such an important form of social currency: People give presents to celebrate and reward one another, and use them as apologies, distractions, and bribes. But humans aren’t the only ones who give gifts for selfish reasons.

A new study authored by scientists from the University of Exeter and the Max Planck Institute for Chemical Ecology and published last week in PLOS ONE, has found that a male cricket’s postcoital “nuptial gift” to his mate is really more of a gift to himself. The gift, a gelatinous blob called a spermatophylax, can manipulate a female cricket into becoming a mother.

Nuptial gifts are a common feature of courtship in the animal kingdom, especially for insects. Before, during, or after sex, male animals present their mates with food or pretty objects. Gifts of food deliver an extra boost of protein or nutrients. Those nutrients will be passed on to the female’s eggs, making the next generation a little hardier and stronger.

But the nuptial gift of the decorated cricket, Gryllodes sigillatus, does none of these things. The sweet and chewy spermatophylax has no nutritional value whatsoever. “They’re a sham,” Illinois State University entomologist Scott Sakaluk told Nautilus last year. The gift is “the equivalent of a gummy bear,” he said. “Gummy bears are really tasty, but you can’t live off gummy bears.”

A spermatophylax doesn’t just fall out of the sky; the male cricket has to devote a lot of resources to making it. And he wouldn’t do that if it weren’t worth his time. So what’s it for?

Manipulation. It looks so innocent, but the gummy bear is a Trojan horse. By eating the male cricket’s gift, the female cricket unwittingly takes part in ensuring her tricky mate’s legacy.

Scientists already knew about the first phase of the subterfuge: distraction. After mating, the male cricket deposits a small packet of sperm and a big nuptial gift at the tip of the female’s ovipositor. (You can see both in the image above; the spermatophylax is the big, clear blob, while the sperm packet is smaller and cloudy.)

Unlike the gift, the sperm packet actually is nutritious, and the female will eat it if she gets the chance. But before she can get to it, she finds the gift. It can take her up to 50 minutes to eat the cricket candy—which is, on average, as long as it takes for the sperm to transfer into her body. The bigger the gummy bear, the better the chance that a male’s sperm will be successful in their quest.

But the deception goes so much deeper. In their study published in PLOS ONE, the researchers reported that compounds in the cricket’s nuptial gift seem to change the female cricket’s body and behavior.

The team found two types of proteins in the spermatophylax. One is protective, and keeps the female cricket’s gut from digesting the second protein. That protein may have two purposes: first, to beef up the female’s reproductive system, and second, to kill her sex drive and keep her from mating with anyone else.

So the cricket’s nuptial gift may be less like a gummy bear and more like a gummy vitamin—one the female cricket has no idea she’s taking.