Traumatic Insemination – Male Spider Pierces Female's Underside ...

You can see it happening in the videos below. In the first, the male spider bites and incapacitates the female. In the second, he hooks the conductor of one pedipalp around the embolus of another and, with rotating motions, drives it into the female. These videos aren’t pretty – you’ve been warned.

When most spiders mate, the male ejects sperm into the female’s vulva, and she stores it in a special pouch called the spermatheca. These pouches allow females to control when she fertilises her eggs, by voluntarily shunting sperm onto them before she lays. It also means that the last male to mate with her typically sires most of her offspring, because his sperm flushes out those of earlier liaisons.

This system means that there’s a fever-pitched sperm competition between males. Different species have evolved bizarre adaptations to get an edge in these conflicts. Some guard their mates after sex. Others leave behind “mate plugs” – chastity belts that block the female’s genitals. The males of one species take this to an extreme, by spontaneously dying during intercourse and turning their entire bodies into a mating plug.

But H.sadistica‘s brutal sexual practice allows it to bypass the competition altogether because the male’s sperm can travel directly to the female’s ovaries through her bloodstream. By wresting control of fertilisation from females, males ensure that when they mate, their sperm isn’t shunted aside at the risk of later removal. The female’s genitals support that idea, for her spemathecae have atrophied and are extremely small. Since the male doesn’t ejaculate in the usual place, she has no need to keep around storage space for his sperm.

The wounds don’t seem to harm the female, and Rezac never saw blood leaking from the punctures. If the females are put off by their repeated stabbings, they don’t show it. Within days, they are usually ready for a new mate.It might even be positively beneficial for the female to mate with males who practice traumatic insemination. The sons of such a partnership would themselves be better at circumventing the female’s sexual stores and having more offspring of their own.