How Oral Sex Can Save Male Spiders

If you think dating is tough, it’s nothing compared to what male spiders have to go through – where getting laid can often mean getting eaten shortly after – a known practice that has given the Black Widow spider a rather fearsome reputation. Male Black Widows will sometimes catch and wrap a large insect in the web as a parting gift, a food item to distract their mate while they make their escape and avoid becoming the main course themselves. The Darwin’s Bark Spider (Caerostris darwini) has another idea for staying alive as long as it can. According to a recent report by a team of arachnologists (those who study spiders), male bark spiders may actually be providing oral sex to their female partners in order to avoid being eaten.

Simona Kralj-Fiser, a researcher at the Slovenian Academy of Sciences and Arts, led her team on a two-week field survey at the native home of this species in Madagascar, where they were able to observe the courtship of this intriguing species. The Darwin’s bark spider is already a popular interest by many in the field, considered to be one of the master artisans when it comes to web building – where they are said to build some of the most durable webs of any arachnid – spinning orb webs with anchor lines up to 82 feet in length. After limpet teeth, their silk is the second toughest known biological material, 10 times stronger than Kevlar.

Named for their resemblance to lichen, the bark spider is a rather recent discovery, found only in 2009, and so very little as actually known about this species’ ability to reproduce. This is what Kralj-Fiser and her colleagues initially came to investigate. They reported their findings last week at the annual Ethological Society’s “Causes and Consequences of Social Behavior” conference in Hamburg, Germany.

Like so many other male invertebrates, male bark spiders are significantly smaller than their female counterparts, and therefore are opportunistic maters. They were even observed mating with some of the younger females who had not yet grown fang cuticles and whose exoskeletons had not yet hardened over their bodies. For anyone who despises spiders already, this is probably the last thing you may want to read – but it is the result of an evolutionary advantage that males of this particular species are given over the females. Male bark spiders develop at faster rates, allowing them to defend their female partners as they compete against each other for rights to breed. However, this period of dominance is rather short lived.

“When a female’s cuticles harden and she can move and attack, she is able to prevent long copulations,” Kralj-Fiser explained on the New Scientist’s blog Zoo Logger.

At the conference, Krajl-Fiser explained a rather startling (although, perhaps unsurprising) statistic: When the females they observed reached their full maturity, 76 percent of them behaved aggressively towards the males. In about 35 percent of the observed cases, the females ended up cannibalizing their mates shortly after having sex. Despite the black widow spider’s reputation, females have only been shown to cannibalizes their mates only two percent of the time – quite a surprising contrast.

Recent research efforts have demonstrated that black widow males have developed the ability to sniff out their mate’s appetite for blood, allowing them to escape in time, the bark spider doesn’t appear to have adapted this useful ‘spidey-sense.’ The answer might cause you to never watch nature shows quite the same way again:

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

The researchers proposed a theory that by simply ‘going down’ on the female, the male bark spider keeps its mate calm before and after mating, a practice that helps ensure that the male won’t become dessert. Further supporting their theory is the observation that the males did not perform the same act on any of the younger, harmless females.

However, the researchers have noted that this proposal is hardly the only explanations for this ritual. For one example, female Darwin’s bark spiders will often mate with several males throughout their lives. Past research on other species of spider reveal that the males will often take measures to keep their mate content, as male black widows are known to do. However, this has been seen in non-cannibalistic species as well, as a way to be sure that they are not abandoned for another mate.

If you think the oral sex hypothesis sounds strange, females of the Leucauge mariana orb weavers seem to enjoy what arachnologists call a “hairy kiss.” A male spider who is a good ‘kisser’ has noticeably thick hairs on his mandibles which it uses to stimulate its mate. The mates of the successful ones are much more likely to stay around. For when it’s really serious, she will join him in forming a “genital plug,” in which a type of lubricant similar to that used for webs will signal that she has been claimed and prevent other males from having sex with her. As strange as it sounds, this has long been proposed as the arachnid equivalent to marriage.

Perhaps the bark spiders in performing this ritual are actually doing something similar to a genital plug rather than an oral sex act, but the research has yet to fully verify either claim.