Male spiders give ‘oral sex’ to keep from getting eaten –study

^{A male bark spider (upper left) keeps a careful distance from its larger potential female mate.}

Sexual cannibalism is when a female organism eats the male before, during, or after they have sex. It’s a well-documented occurence in spiders and insects, and is the reason why multiple species are nicknamed “black widows.”

 

Scientists have recently discovered, however, that male Caerostris darwini—commonly known as the Darwin’s Bark Spider—have developed a technique to escape this untimely death.

 

One way that male Darwin’s bark spiders escape being eaten is by performing oral sex on their female partners.

 

Darwin’s bark spiders are found in Madagascar. Much of their mating behavior is unknown, so a group of researchers spent two weeks studying them in hopes of shedding light on the subject. Simona Kralj-Fiser, from the Slovenian Academy of Sciences and Arts, led the team.

 

They found that females mated with multiple males and that males were highly competitive for mates. They also found that 76 percent of females were aggressive towards males and that 35 percent of females ate their mates after copulation.

 

Males developed two ways to prevent getting eaten. One way was to hang out around younger females instead of fully-matured adults. When the female spider is young, she’s still soft and relatively defenseless.

 

“When a female’s cuticles harden and she can move and attack, she is able to prevent long copulations,” Kralj-Fiser explained.

 

But when it comes to mating with adult spiders, the story is different.

 

Researchers noted that during copulation, the males pressed their chelicerae (the pair of fang-like mouthparts usually used for grasping or piercing) to the females’ epigyne (the external genital structure), something that they didn’t do when mating with younger females.

 

“Males nibble on female external genitals using their fangs, and then we observed that there was a liquid coming out of the fangs,” said Kralj-Fiser. “We do not know what this liquid is, but it looks like digestive juices, which they usually secrete when eating.”

 

The researchers hypothesized that the “oral lubrication” may relax the females to prevent them from eating the males.

 

The study was presented at the Ethological Society’s “Causes and consequences of social behavior” conference in Germany. — TJD, GMA News