Small males easily become meals for their children

Female spiders are greedy predators, they eat a lot of prey, sometimes even their spouses. There are many hypotheses to explain why female spiders eat male spider meat before or after mating. In a study published in the September issue of the journal American Naturalist, researcher Shawn Wilder and Ann Rypstra of the University of Miami in Ohio found that the answer is probably simpler than what people think. .

Males are more likely to be eaten when they are much smaller than females. The small size of males means they are easily captured. Spider species hellna helluo, the big male never gets eaten while the small male gets 80% of the mating time. Wilder and Rypstra confirmed the results after examining data from many spiders. In relatively small males compared to females, they tend to eat more.

Many studies of sexual predator behavior focus on a few unique cases in which this behavior considers both sex selection and sperm competition. However, when looking at information from many spiders, Wilder and Rypstra found that the size of the male is the same as the female (often referred to as bisexual size), determining how often the occurrence of sexual predatory behavior in one species.

The wolf wolf the Hogna helluo is eating the male meat.(Photo: Shaw M. Wilder)

Shawn Wilder commented: 'We were surprised to find that only a simple feature such as the size of the male and female sizes has such a great effect on the regularity of the behavior. eat mates'. In many cases, the behavior of sexual predation is not a complex balancing act between benefits and costs for males and females, but the fact is because females are hungry so they eat males when Males are small enough for females to catch.

Evolution does not change this relationship. For example, females do not become larger to eat more males because at that time the males will become too small a meal, not enough for big females. Males do not grow smaller to eat more as they will not have the opportunity to mate many times. In addition, sexual predation behavior is probably a by-product of the evolution of adult females and small males in a carnivorous species.

Refer:
Shawn M. Wilder and Ann L. Rypstra, "Sexual size dimorphism predictions of frequency of sexuality within and among species of spiders" American Naturalist (2008) 172: 431