Male black widows prefer to mate with females who have just eaten (so they don't become her next meal)



Male black widow spiders select mates who have recently fed to avoid getting eaten themselves, according to scientists.

Female black widows are well-known for feeding on their partners immediately after sex.



Now researchers believe the male of the species deliberately seeks out a 'fat' female who is full-up before mating.

A black widow spider couple clings to a web. The male of the species deliberately seeks out a 'fat' female who is full-up before mating, scientists now believe

The findings by scientists at the University of Nebraska reveal a rare turnaround in the sexual power struggle in which the male of the species has the advantageous power of selecting a mate.



Researcher Eileen Hebets said: 'Most of the time people focus on females. It's much less common to think of males as a potential source of selection.'



The scientists travelled to Arizona to study the North American black widow, Latrodectus hesperus.

There, they discovered that male black widows can detect tell-tale chemicals on the webs of females - these let them know if they are well-fed or not and therefore improves their chances of not getting eaten.



Another advantage is that in choosing a larger lady, the male black widow is increasing the chance of a mate with a large number of eggs.



Lead researcher Chad Johnson told Inside Science News Service: 'It's a double whammy.'

He explained that the danger of mating is so great for males, that nature forces them to be extra selective.

'The black widow male is not at all complicit in his own demise. He's making the best of a bad situation'

Dr Johnson and his team tested this with four experiments.



The first saw that males were more likely to court on the empty webs of well-fed females; the second added the females to their webs and again the males chose them.



The third experiment saw the scientists put hungry females on the webs of well-fed females and vice versa - the males showed no particular preference.



Lastly, the researchers rolled webs from both well-fed and hungry females onto separate sticks and watched the males choose the 'well-fed web' sticks.



From this, they concluded the webs must contain a chemical left by a well-fed female that is attractive to would-be suitors.

