Female brown widow spiders get grumpy in their old age. They demand more courtship displays from males, and are more likely to eat the suitor. Despite that, given the choice males will pursue them instead of younger, more fertile females who won’t eat them.
For male brown widow spiders (), sex can be lethal. Like other spiders, such as black widows, females sometimes kill and devour males after sex. This is especially true of older females.
A team led by of the Agricultural Research Organization near Tel-Aviv, Israel, introduced virgin males to adolescent females, young adult females and older adult females. All were able to reproduce.
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57 per cent of males that mated with older females were cannibalised, as were 48 per cent of those that mated with young adults, but adolescent females never ate their partners. Nevertheless, males courted older females for longer than they did young females, and spent hardly any time wooing adolescents.
Inexplicable choice
Sometimes a male brown widow stops copulating and performs a somersault, pushing his abdomen into the female’s mouth. This can get him eaten. Harari found males almost always somersaulted when mating with older females, but rarely did when mating with adolescents.
In a separate experiment, males were given a choice of females. They were more likely to approach and mate with older females, even though they were less fertile.
“In some species of spiders, males take measures to avoid being eaten,” says Harari. They may orally lubricate the female’s genitals or prolong courtship. “However, in L. geometricus, not only do males give up their future reproductive success by being cannibalised, they also seem to choose the females that are more likely to cannibalise them.”
Males could benefit from being eaten if it led to longer sex, allowing them to transfer more sperm. But somersaulting males, who are more likely to be eaten, had shorter sex sessions.
It may be that older virgin females produce more pheromones to attract males. If so, older females are essentially tricking males into thinking they are more fertile than they really are.
“Old females are more desperate for mating, thus they may put more effort into advertising their availability,” says Harari. “It’s possible that males are duped into mating with them.”
However, there is an alternative explanation, says  of Arizona State University. Male brown widows prefer to court larger females, which are generally in better condition and less likely to eat them. “Without body size accounted for in these models, it is entirely possible that we could be viewing adaptive male courtship preferences for well-fed animals, rather than non-adaptive courtship preferences for old females.”
Animal Behaviour
