Male spiders eaten after sex carefully choose mating partners, study says | The independent

Male spiders likely to be eaten by their mates after sex are significantly more picky about mate selection than the females, a new study finds.

In many species, the males tend to sleep around to maximize their chances of having children as they have almost abundant sperm. Females often only have a limited amount of eggs and are therefore usually a bit more picky about who they have sex with.

However, researchers suspected that if the males were likely to have only one chance to pass on their genes — due to the high risk of death that the academics described as a form of forced “monogamy” — they might be a little more critical.

They wanted to test their theory by putting colonial orb-weaving spiders, Cyrtophora citricola, together in a room and waiting to see what happened.

A paper in the Plos One diary of their findings, called Restrained males and seductive females in the sexually cannibalistic colonial spiderdescribed a typical sexual encounter between two spiders.

The female approaches the little male until she is about an inch away. The male then rushes in and “inserts his pedipalp (the male organ) into the female’s genital opening”.

“The female bites the male’s abdomen while the pedipalp is still attached. The female pulls the male to her mouthparts and the pedipalp comes off. Copulation usually only lasts a few seconds,” it added.

The results of the study confirmed the theory that men were the pickier of the two.

Researcher Eric Yip, of Ben-Gurion University of the Negev, Israel, said: “We found that males prefer to court and mate with younger, fatter, and therefore potentially more fertile females.”

In contrast, the females showed “no mate choice related to male diet or age,” the paper said.

Of the 80 pairs of spiders courting, 32 had sex within 30 minutes and 21 of the males were killed and eaten.

Seventeen men had sex once, four managed to do it twice. The 11 male survivors had sex only once. The females were less likely to eat poorly fed males.

The paper said that “post-copulatory cannibalism … forces monogamy in most men”.

It added that the males inadvertently increase their chances of being eaten by breeding with larger females.

“These findings suggest a co-evolutionary cycle: cannibalism by women led to mate choice by men, who in turn may select for more aggressive women who court,” it added.