Oral Sex is Saving Male Spider Lives

"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 said at the conference.

The theory is that this action helps keep the female mate calm both before and after mating, helping to ensure that the male doesn't become a post-sex snack. Supporting this theory is the fact that males don't perform this act on the younger harmless females.

However, it's important to note that there are other explanations for this behavior, too. For example, Darwin's bark spiders often mate with multiple males in their lifetime. Past research has shown that the males of some spider species will actually work to keep their mate happy, even if that mate is not cannibalistic, in order to ensure that she does not go off to mate elsewhere.

Female Leucauge mariana orb weavers also seem to enjoy a hairy kiss. If a male winds up being a good 'kisser,' stimulating his mate with thick hairs on their mouthparts, she is more likely to stick around. She will even sometimes help him form a "genital plug," which essentially prevents other males from having sex with a claimed female spider. It's a strange way of tying the knot, but experts have long compared this kind of mutual plug formation to marriage.

And that could also be what the bark spider's "oral sex" act is really all about. The liquid a male secretes may not be a lubricant at all, but instead a kind of glue, helping facilitate the creation of a plug that ensures the mother of his children doesn't go running off with another man.

However, much more observation and research will be needed to determine what, if not all, of these theories hold true.

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