Male mantises sneak up on females when the wind hides their footsteps
For some male insects and spiders, courtship can end with being eaten. So they have evolved tricks: males of one mantis species approach while gusts mask their noise, Pisaura spider males play dead, and orb-weaver males wait until the female is busy with a meal. In the Chinese mantis, up to half of matings end in cannibalism.
Biologists define sexual cannibalism as one partner, usually the female, eating the other before, during or after mating. It turns up across spiders and other arachnids, praying mantises, some crickets and cockroaches, several crustaceans and snails, and, rarely among vertebrates, green anacondas, whose females outsize the males. It is most common where females are much bigger than males, and it is thought to reflect sexual conflict: the two sexes' reproductive interests pull in different directions.
Several explanations compete. The adaptive foraging idea says a hungry female weighs a male's food value against his worth as a father. Evidence backs it in places: females of the mantis Pseudomantis albofimbriata gain in fertility and body condition, and in some spiders hungry females that eat a small male before mating with a larger one produce bigger, more successful egg cases. Critics once argued males make poor meals, yet wolf spider males turn out to contain proteins and lipids that crickets lack. A rival idea, aggressive spillover, holds that the fiercest hunters simply attack anything, suitors included. Others see mate choice at work, with females eating weak or small males, and a mistaken identity theory remains unproven because it is so hard to separate from the rest.
Some males may even benefit from being eaten, feeding the female and raising the odds their sperm is used, although such self-sacrifice has been reported in only six genera of orb-weaving spiders and much of the evidence is anecdotal. Sagebush cricket females take a partial approach, eating only the male's wings and sperm package.
The phenomenon may reach further than thought. A recent study described a female green and golden bell frog preying on an adult male during breeding season, and the authors argued that amphibians, where females are often larger and gather with males to breed, deserve a closer look, while stressing their sample was small.
Source: Sexual cannibalism
