If you thought your last hookup was awkward, spare a thought for the male redback spider, whose one and only romantic encounter ends with him being devoured by his partner. And apparently, he's the one who initiates it - by performing what researchers have dubbed a 'self-sacrificial somersault' into her jaws. Because nothing says 'I love you' like offering yourself as a post-coital snack.

The redback, also known as the Australian black widow, is one of just two widow spider species where males typically mate with a single female - a lifestyle choice that seems to have some serious drawbacks. During the act, the male uses his pedipalps (two arm-like appendages, for the non-arachnid enthusiasts) to transfer sperm to the female's two sperm storage organs. Then, he flips his abdomen directly into her mouthparts and constricts his abdomen to make it harder for her to get a grip. 'He's pumping sperm, he flips his abdomen right over into her mouthparts and then he constricts his abdomen … to make it hard for the female to get a purchase on his abdomen,' explained Cor Vink, an associate professor and spider expert at Lincoln University in New Zealand. 'That lets him survive the first mating.'

Why risk it? The somersault is thought to maximize reproductive success, but it's a gamble: if the male gets eaten before transferring sperm to the second storage organ, he misses out on siring half the offspring. 'Ideally, males should mate with the same female two times because females have two separate sperm storage organs,' said Kardelen Özgün Uludag of the University of Hamburg, first author of the study. 'A male needs to inseminate and plug both of them, so that he can sire all of the offspring she produces. If a male dies after the first mating, another male can mate with the same female and then half of the female's offspring would be from the second male.'

Some quick-thinking males have found a loophole: mating with immature females that haven't yet learned the fine art of partner consumption. But the redback, which is widespread in Australia and has been unintentionally introduced to New Zealand, Japan, and the United Arab Emirates, is a bit of an outlier in the widow family. Its close relative, the New Zealand katipō, doesn't practice sexual cannibalism at all. 'In the katipō, the male inseminates the female and runs off the web - that's the same for most widow spiders,' Vink said. 'The term widow is actually a misnomer.' Indeed, of the 31 widow spider species, only redbacks and brown widows typically show this sacrificial behavior.

In a study published in Biology Letters on Wednesday, German researchers set out to find the genetic basis for this somersaulting suicide. They bred female katipō with male redbacks and found that nearly half of the third-generation offspring also somersaulted, pointing to a specific location on the X chromosome. 'It is quite remarkable that a highly complex phenotype such as somersaulting, which may lead to partial reproductive isolation, can have such a simple genetic basis,' the researchers noted. 'Our work shows that this highly complex cannibalistic behaviour can evolve rapidly, with very few genetic changes,' Uludag added.

This isn't just academic curiosity: in New Zealand, Vink has found evidence that native katipō and invasive redbacks are interbreeding in the wild. 'This is a concern because we could lose our endemic protected species just through hybridisation,' he said. Katipō diverged from redbacks about 100,000 years ago, so the fact that the behavior was lost that quickly is 'really neat,' according to Vink, who called the paper 'elegant.' 'The more we know about the interbreeding, the more we know about what we can do to combat redbacks and katipō interbreeding in New Zealand,' he added. So next time you're complaining about your dating life, just be glad you're not a male redback - unless you're into that sort of thing.