Praying Mantis Sex and Cannibalism

Carolina Mantids Mating
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The female praying mantis is often painted as an evil seductress, a cannibalistic lover that lures males closer, only to eat them after mating. Is her reputation deserved? Does praying mantis sex always end in cannibalism of the male?

Female Mantis Shaming or Truth?

Rumors of the praying mantis' cannibalistic tendencies began when scientists observed their mating behavior in a laboratory environment. Entomologists would offer a captive female a potential mate and would quite often be horrified to watch the female bite the head or legs off the smaller male—sometimes even before mating. After the male had served his copulatory purpose, he was nothing more than a good meal for the female and her upcoming offspring. For a long time, these observations of praying mantis sex in the lab were thought to be the way things were in the mantid world

Much Less Common in the Wild

After scientists started observing praying mantis sex in a natural setting, the story had a different ending, which is good for the males. When unconfined by laboratory terrariums (and not starving), the majority of praying mantis mating ends with the male flying off unharmed. By most estimates, sexual cannibalism by praying mantis females occurs less than 30 percent of the time outside the lab. Those are better odds for the fellows than what had been seen in the lab. Praying mantis sex, it turns out, is really a rather romantic series of courtship rituals and dances that typically ends satisfactorily and safely for both parties involved.

How Males Choose Females

Given a choice between females, male praying mantises will move toward females seen as less aggressive (i.e., ones they hadn't just seen eating another male) more often than the more aggressive females.

The males also tend to prefer to mate with females that appear fatter and more well fed than others, as the skinnier and hungrier mantises are more likely to eat their mates during or after sex. This could also point to the males being more attracted to females that are healthier, for the betterment of their offspring. 

Advantages of Beheading Your Mate

There is a decided advantage for the female if she does decide to behead her lover. The praying mantis brain, located in his head, controls inhibition, while a ganglion in the abdomen controls the motions of copulation. Absent his head, a male praying mantis will lose all his inhibitions and consummate his relationship with wild abandon.

And what if she's hungry? For certain, a slow-moving and deliberate predator like the praying mantis is not going to pass up an easy meal. If a male makes the unfortunate choice of a hungry female for a mate, he's probably going to be toast after they've mated.

Either Way Could Benefit the Males

A twist: Being eaten by the female paradoxically may mean that that particular male has more of his genetics making it to the next generation if more of his sperm fertilize his mate's eggs while she is eating parts of him. More eggs are laid by females who eat their mates as well (88 vs. 37.5 in one study). However, if a male can mate more than once, that also increases his odds of having his genetics passed on.