In one of the most spectacular displays of sexual cannibalism, male praying mantises can get their heads ripped off while copulating with females. But now, researchers have discovered that starving females will sometimes trick males into thinking they’re full of eggs waiting to be fertilized... but then she eats him without letting him mate with her at all. Skip dinner and go straight for sex? For some mantids, it’s the other way around. The work was published in Proceedings of the Royal Society B this week.
“This is the first evidence in support of the Femme Fatale hypothesis, which posits that female mantids in poor condition might dishonestly entice males in order to eat them rather than mate with them,” Katherine Barry of Macquarie University says in a news release.
Recent work found that healthy, well-fed female mantids sometimes deceptively signal to males, luring them in only to consume them. But starving females have the most to gain from this duplicitous trick. To better understand this underhanded system, Barry collected 100 or so false garden mantises (Pseudomantis albofimbriata) from various sites around Sydney. For about six weeks, 24 females were assigned to one of four feeding regimes: good, medium, poor, or very poor. Then she placed cylindrical cages containing these females in large field enclosures on the university campus; the cages were covered with two layers of mesh so you couldn’t see inside them, but the chemical signals they produced could escape. Then Barry released adult virgin males into the field. Of the 78 males released, 55 of them were found on female cages. The number of males found on specific cages was used as an indicator of female attractiveness.
Starving females aren't as desirable to males since they produce fewer eggs and they’re more aggressive, yet "very poor females" attracted significantly more males in total than females from any other feeding treatment.
Barry thinks that the starving females are able to attract so many suitors by using chemical deception: They’re likely increasing the quality or quantity of pheromone emission. Making and releasing pheromones isn’t cheap, but consuming just one duped male improves body condition by 33 percent and fecundity by about 40 percent.
