Female praying mantises have a habit of killing and eating their partners during sex, which sucks for the male. Or does it? A fascinating new study shows this sacrifice is actually giving the males a distinct reproductive advantage. Sexual cannibalism among praying mantises is well documented, but scientists have debated the reasons for it.
The female praying mantis is known for cannibalistic mating behavior: biting off the head or legs of her mate and eating them. This behavior, which occurs in less than 30 percent of all mating sessions in the wild, may have evolutionary advantages for the praying mantis species. Rumors of the praying mantis ' cannibalistic tendencies began when scientists observed their mating behavior in a laboratory environment. Entomologists would offer a potential mate to a captive female; after mating, the female would bite the head or legs off the smaller male. For a long time, these laboratory observations were considered proof of mating habits in the mantid world. However, after scientists started observing praying mantis mating in a natural setting, the behavior changed.
Insect Sex: Watch Headless Praying Mantis Continue To Mate After Being Decapitated by Female
Sexual cannibalism is when a female cannibalizes her mate prior to, or after copulation. The adaptive foraging hypothesis,  aggressive spillover hypothesis  and mistaken identity hypothesis  are among the proposed hypotheses to explain how sexual cannibalism evolved. This behavior is believed to have evolved as a manifestation of sexual conflict , occurring when the reproductive interests of males and females differ. Females of cannibalistic species are generally hostile and unwilling to mate; thus many males of these species have developed adaptive behaviors to counteract female aggression. Sexual cannibalism is common among insects, arachnids  and amphipods.
Nothing stands between a male praying mantis and his need to get laid, not even losing his head to a hungry mate. Now, a particularly gruesome video shows that, even without a head, a male mantis was still able to mount his female and complete the mating process. Nearly everyone knows at least two facts about praying mantises; that the female eats the males after having sex, and that it's illegal to kill one of these alien-looking creatures. While the latter fact is actually completely false shocking, I know , it is true that hungry females will consume her mate in effect to have enough energy to incubate the couple's fertilized eggs.