Starving mantis females lie to make a meal of a male
Despite common lore, most female praying mantises — any one of several species of the insects — don’t cannibalize their male mates. Among false garden mantids, for example, a common species in Australia, only about 40 percent of matings end in death for the guy. And there are a few ways a male can reduce his chances of being eaten, says mantis researcher Katherine Barry of Macquarie University in Sydney, one of which is to approach an unsuspecting female from behind. Those that dismiss Barry’s advice might find themselves without a head (though he may still get to mate; with his body free, a male mantid can pull his body around to complete his transaction, Barry says).
But following Barry’s advice might not be as easy as it sounds. That’s because starving females are liars, Barry has discovered. Her research appears December 17 in the Proceedings of the Royal Society B.
For her study, Barry collected false garden mantids from various places around Sydney, mostly among the basket grass in a park near her university. Back in the lab, she split the females into four groups and fed them different diets, producing mantids ranging in condition from very poor to good. Barry then set up a mantid mating game, with females obscured from sight and males allowed to choose based solely on scent.
Among females in the three best-fed groups, the amount of food a girl mantid had received was tied to her attractiveness to the males. But the most attractive females by far were those in the last group, the ones who had been given the least food, were in the worst shape and were the least fertile.
Those starving females, Barry says, invest their limited resources in producing chemical cues — pheromones — to lure males in. The investment can easily pay off. “The consumption of one male improves body condition by approximately 33 percent and fecundity by approximately 40 percent,” she writes in her study.
Earlier research showed that female mantids of this species that are in the best condition do not cannibalize their male partners, but 90 percent of girls in the worst condition will — and only half of their encounters end in a male getting to mate. Combined with the results from the new study, this suggests that the starving females are “deceptively signaling” (what we’d call lying) that they are in good condition and have plenty of eggs, Barry writes.
And false garden mantids may not be the only liars, Barry says. “Lots of mantid species are similar,” she notes, and she expects there may be more femmes fatales among those other praying mantises.