The benefits of cannibalism
Spiders that cannibalize potential mates have bigger broods, according to new research published last month (July 27) in Animal Behaviour. Females of some spider species eat males without copulating with them first, but exactly why has been a mystery. To find out, researchers at the University of Pittsburgh captured local funnel-web spiders (Agelenopsis pennsylvanica) and tracked the fitness of aggressive females, who tend to eat more males, versus more passive females.
A popular hypothesis is that the choice to eat a male or not is due to females gauging whether they would be more useful as mates or meals, but no link was found between aggressiveness and female or male body size. Instead, it was found that when females ate males, more hatchlings emerged from thicker eggs sacs. Hatchlings have to tear their way out of the egg sacs, and while cannibalistic females were no more ...
