Imagine you are a horny male redback spider. You might be a small guy—a fraction of her size—but unlike some, you don't have a complex about it. You're just happy to be there, "there" meaning the haphazard snarl of a web of a female redback spider. Only 20 percent of male redback spiders ever mate, so you're already feeling lucky. You know that the climax of your life has arrived, meaning your climax.
You approach the spider and insert into her one of your two pedipalps, a pair of leg-like appendages that dangle by your mouth and hold your sperm. Then, as is custom, you initiate a parkour sequence. After doing a headstand, you flip yourself on your back, landing your body between the female's fangs. There, your palp still inside her, she begins to chew on you. If you survive this—which you often do thanks to your ability to squeeze your waist really small so her fangs can't immediately impale you—you two take a break. Then you're back in action, inserting your second palp in her and sliding cleanly into headstand number two, followed by that somersault, followed by more chewing. This time you let her finish you off, meaning eat you entirely. But you don't have a complex around this either. You have completed the work of your life, ensuring that the batches of eggs she will soon lay are all fathered by you, who, at this point, have departed this mortal coil, digested and excreted by your large and lovely mate. "This is the mating ritual of L. hasselti," Kardelen Özgün Uludağ, a PhD student at the University of Hamburg in Germany, wrote in an email.
If this for some reason is hard to imagine, perhaps the following video will help.
The sexual stylings of the redback spider, also known as the Australian black widow, are unusual, even for spiders. Sexual cannibalism, meaning the practice of eating your mate before, during, or after sex, is common in spiders and other invertebrates. This often looks like a female spider actively killing and eating her conveniently located mate. But male redback spiders literally somersault to their own death. Impaling yourself on the fangs of your lover without being asked might seem an odd evolutionary strategy. But it helps guarantee that a male can mate to completion, which means he will father more offspring. A group of researchers investigated the genetic basis of this singular somersault, as well as the male's snatched stomachs, in a paper recently published in the journal Biology Letters.
Although the redback spider lives in Australia, the authors of the new paper are from Germany. They first became interested in the redback spiders after learning about their closely related sister species, the katipō, which lives only in New Zealand. Unlike the redback spiders, katipō spiders of both sexes mate with multiple spiders, none of whom seem interested in sacrificing themselves. "What makes this system so intriguing is the fact that we are dealing with two species here, which are very closely related," Henrik Krehenwinkel, a researcher at Trier University and an author on the paper, wrote in an email. Although the two species diverged less than 100,000 years ago, they display totally different mating behaviors. "This is very uncommon in animals," Krehenwinkel added.
The researchers realized these two spider species offered the perfect opportunity to try to identify the genetic origin of the sacrificial somersault. To do this, the researchers bred female katipō spiders with male redbacks, pairing easy-going females with the males with a death drive. (The pairing did not work in reverse; pairing males who had no interest in sacrificing themselves with females that expected them to produced, in the words of the researchers, aggressive responses.) The male redbacks still insisted on somersaulting into the mouths of the katipō females, and were presumably surprised to leave such encounters alive.
The researchers then paired the hybrid offspring in 104 mating experiments, looking to see which male spiders performed the sacrificial somersault or exhibited abdominal narrowing. Their results suggested that the gene that controls the somersaulting is located at a single point on the spider's X chromosome (male and female spiders both have two X chromosomes, but males only have one complete set of DNA in each chromosome, whereas the females have two.) The researchers were surprised that "that the somersaulting behavior has a very simple genetic inheritance," they wrote in an email. But the abdominal narrowing did not appear to have such clear genetic origins, suggesting that the trait might emerge from locations far apart on one chromosome or even from different chromosomes.
Both the redback and katipō spiders belong to the genus Latrodectus, often called the widow spiders. The three species of American black widows, spiders that have distinctive red hourglass markings on their back, belong to this group. Despite their scary reputation, however, black widows rarely kill the male after mating. Although they are the most venomous spider in North America, their bites are only high risk for young children and elderly people, per Smithsonian. Redback spiders have even more potent venom, which is unsurprising given the overall vibe of animals in Australia.
Both redback spiders and katipō spiders can be found in New Zealand, where they hybridize of their own accord. This could threaten the katipō, which is a protected species, a spider expert told The Guardian. In other words, sacrificial somersaults could be the latest dangerous craze sweeping the nation. Yet we must remember that to some spiders, sexual cannibalism is simply their culture. And who are we to kink shame?
