Praying mantis do this, and so do females of some beetle species, but spiders in particular are known for it: sexual cannibalism is a reproductive strategy. The female eats the male after or even during mating. “He” was still able to reproduce and “she” gets energy and nutrients for egg production. The body and investment of the male life also serve his successful reproduction.
Better yet for him and for the survival of his genes it would be to have more than one chance to do so. It can produce more offspring, which should favor the evolution of appropriate posture and body traits for flight after mating.
Males of the spider species have a special mechanism Philoponella prominens developed, is now reported by an international research team in the journal Current Biology. After insemination, he catapults himself to safety with his front legs. She is missing a meal, but the ability of the female spider to get up immediately can at least serve as a clue that she has chosen a suitable mate.
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Super fast rescue from cannibalism
A research team led by Shichang Zhang from Hubei University in Wuhan, China, studied mate selection in this spider species. Animals live unusually for spiders in communities of up to 300 individuals in a network complex with many individual nets in it. “We noticed that the pairing ends with a catapult flight so fast that conventional cameras can not record details clearly,” says Zhang.
Using high-resolution camcorders, the team set an average speed of about 65 centimeters per second for catapulting male spiders. Some reached almost 90. They accelerated at an average of about 200 seconds meters per second, which is roughly equal to the acceleration of a professional cyclist. Spiders thus achieve higher values than missiles, sleds, and airplanes in aerobic maneuvers.
Men use a mechanism that has not yet been described. They are folded over a joint of both their front legs and pressed against the female with their legs bent. There are no extensor muscles in the spider’s leg for this joint, but hydraulic pressure is created, which leads to sudden opening when the spider man detaches, the researchers explain.
In the animal world there are other examples of such crackling mechanisms, for which energy is stored slowly, which then allows extremely fast actions or reactions, similar to the operation of a catapult. Praying mantis, for example, use their front legs to catch prey. Jaw ants also close their jaws to get away from predators. “However, such super-fast actions as a means of avoiding sexual cannibalism have not yet been reported,” the researchers write.
Choosing suitable partners
After 155 mating observed, almost all males were cast by females in this way and survived. Only three men made no attempt to escape. They were caught and eaten by women. This is exactly what happened to the male spiders, in which the scientists blocked the jump mechanism with a fine brush. In 30 trials, all were eaten by females. These results clearly showed that catapulting behavior was an essential component of male mating behavior. The strategy of avoiding the spider woman bite was developed under the strong predatory pressure of females – their sexual cannibalism.
“Women can use this behavior to judge a man’s quality during mating,” Zhang suspects. If a man can not catapult, they kill him. If he consistently achieves spectacular escape, the animals mate up to six times, they accept him as a partner.
In future studies, the team wants to investigate the role of catapulting ability in male mating success.