Threesomes are a tricky business - especially if you're a male wolf spider.

The spiders' kinky three-way sex can go on for as long as four hours and the third wheel waits for the other male to woo the female before he joins in.

These unholy unions are believed to be an evolutionary advantage for the male spider as it reduces the chance of him getting eaten alive by the bloodthirsty female.

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Matthew Persons, a professor of biology and ecology at Susquehanna University in Selinsgrove, Pennsylvania said that threesomes have an evolutionary advantage for the 'third wheeling' male wolf spider

THE ADVANTAGE OF BEING A THIRD WHEEL By joining a mating pair the third wheel avoids wasting energy on wooing the female. Courtship also makes spiders vulnerable to predators. If a female takes a disliking to the male she can cannibalise them before even having sex. Even after mating, if she's left unimpressed she's eat her suitor. By joining an already mating pair, the third wheel is reducing the likelihood of getting eaten by both the female and another predator. However, threesomes mean copulation is less successful as the males find it harder to inseminate the female. Advertisement

The 24-legged threesome was first spotted by a professor of biology and ecology at Susquehanna University in Selinsgrove, Pennsylvania.

Matthew Persons noticed the wolf spider ménage à trois in his back garden and took them onto his dining room table to find out exactly what was happening.

'Because they were in my yard, I scooped them up and brought them onto my dining room table and proceeded to take photos and document their positions for the next four hours', Dr Persons told Live Science.

The threesomes involve one female and two males - which is made possible because the female has paired reproductive organs.

Normally wolf spiders mate for 25 minutes to an hour, but threesomes go on for as long as four hours.

'The longer the mating duration, the higher the probability that they get eaten afterwards,' Dr Persons said.

Dr Persons' findings are the first case on record of wolf spiders (Rabidosa punctulata) have three-way sex.

This may have an evolutionary advantage for male wolf spiders because sex is a dangerous business.

Female wolf spiders are likely to cannibalise their suitor if they're unimpressed by their courtship.

Dr Persons' findings are the first case on record of wolf spiders (Rabidosa punctulata) have three-way sex

This may have an evolutionary advantage for male wolf spiders because s ex is a dangerous business. Males often fight each other while trying to attract females but they won't fight if one is already having sex with her

By joining an already mating pair, the third wheel is reducing the likelihood of getting eaten by both the female and another predator.

According to Dr Persons, the third wheel also avoids wasting valuable energy on courting the female - they let the other male do the hard work so they don't have to.

Males often fight each other while trying to attract females but they won't fight if one is already having sex with her.

The threesomes involve one female and two males - which is made possible because the female has paired reproductive organ

Dr Persons saw one male spider lose a leg during mating, although he was not sure if it was the female or the other male who was responsible

However, in terms of sealing the deal, threesomes are not the answer.

'In my direct observations, males showed … sparring, missed insertions, attempts at … insertions into the other male's venter [underside] and attempts to displace the other male during insemination,' Dr Persons said in his study.

Dr Persons saw one male spider lose a leg during mating, although he was not sure if it was the female or the other male who was responsible.

The findings will be published in a forthcoming issue of the Journal of Arachnology.



