Why eating males pays off, for spiders

"The rate of sexual cannibalism increased with male availability, and females were more likely to kill and consume an approaching male if they had previously mated with another male," they added.

"We show that females benefit from feeding on a male by breeding earlier, producing 30 percent more offspring per egg sac, and producing progeny of higher body condition. Offspring of sexually cannibalistic females dispersed earlier and were larger later in the season than spiderlings of non-cannibalistic females."

One theory had also held that females who ate males were simply more aggressive and perhaps better hunters -- but when the males were saved just in time, those females did not produce superior broods, suggesting that the male meals were an important source of nutrition.

The study can be found at: here