Love Hurts

Already think bedbugs are gross? A male fertilizes a female bedbug by piercing her abdomen with his needle-sharp penis, and ejecting sperm directly into her body cavity. And some species of snails produce sharp "love darts," which they "fire" at mates during copulation. Since the darts are covered with mucus, it allows the females to store more of their partner's sperm.

Sometimes, if you truly love someone, you have to let that person go — but the water strider says to heck with that! The males have evolved a way to make sure that females can't escape during lovemaking: Their antennae have prongs, bristles and hooks designed to hold females down by their eyes.

It's not just creepy crawlies that indulge in animal S&M, either. A male cat has barbs on the end of his penis. When he withdraws, it scrapes a female's insides, making her scream and lash out at him. The act is actually required to kick start ovulation, so no pain, no gain.

Kinky Creatures

Causing pain isn't the only weird way that animals do it.

Spiders go so far as to produce their own ropes. The male crab spider, for example, ties the female down with his silk before mating. To be fair, it's something of a safety measure, since female spiders have a reputation for eating their mates.

Group sex is also common among many species. At the end of hibernation, male red-sided garter snakes wake up first, and as soon as they see a female emerge, they all surround her, forming a rolling mass called a "mating ball." Something similar happens with green anacondas — and they can stay massed together for up to a month.

Just Plain Weird

Some animal sex is so bizarre that there are no categories for it. Case in point: Female and male anglerfish become permanently attached to each other. When a male encounters a female — who's ten times bigger than he is — he latches on with his sharp teeth and starts to physically fuse with her body. He ends up sharing her bloodstream, as well as losing his eyes and non-crucial internal organs. Once he's reduced to a pair of testes, the female can get pregnant whenever she wants, making him quite the kept man.

Linda Lombardi is a former zookeeper, college professor and the author of Animals Behaving Badly, a book that grew from her blog of the same name.