Female praying mantises EAT their partners because it boosts fertility

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When a female praying mantis bites the head off her sexual partner, it is probably not out of anger. According to a new study, the mantis' proclivity for devouring her mate may have evolved to better provide for her offspring. In eating the male, a female ensures he continues to provide for their progeny even after death - as food.

'Sexual cannibalism... increases male investment in offspring,' said William Brown of the State University of New York at Fredonia, who co-authored a paper published in the journal Proceedings of the Royal Society B. For the study, Brown and Katherine Barry from Australia's Macquarie University fed crickets dosed with traceable radioactive amino acids to male mantises.

They then allowed the spindly insects to mate. For half the males it turned out to be their final act, while the lucky rest were rescued by their human handlers immediately after pairing. The scientists tracked the flow of radioactive proteins through the bodies of the cannibalistic females, and through their eggs.

In females those who ate their mates, 'there is an increase in the number of eggs produced subsequent to cannibalism,' Brown said.