For some animals, sex involves the ultimate sacrifice. Some species of spider, for example, redefine the concept of a dangerous liaison when the female turns around and devours her mate in a post-coital attack of the munchies. For males, it’s important that this act of sexual cannibalism isn’t in vain and that they die while impregnating the best possible mate. And for the wasp spider Argiope bruennichi, that means no sisters allowed.

She can mate with multiple partners and she can even control whose sperm actually fertilises her eggs. So the male must do everything he can in order to ensure that his genes pass on to the next generation. His job is even more difficult because he can only