Invertebrates inject a bit of romance during sex—by stabbing each other

I stab at thee. But only because i want you to have my babies.

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It's fair to say that we belong to a species obsessed with sex. We are among the only species to have sex for fun, not just for reproduction. For some other species, though, sex is far from fun. In fact, as two recent review papers show, it's a war zone, involving things like penis fencing and love darts.

In 1897, the Italian zoologist Constantino Ribaga discovered a strange organ in female bedbugs, halfway up the abdomen. He suggested that they used it to produce sound, like cicadas. But something wasn’t right: in the bundle of cells underneath this organ, he found large quantities of sperm. How did they get there? At the time, puzzled scientists concluded that males must flood females with sperm, and the female digested the excess—as a “nuptial gift”—using this organ. But this idea was tenuous at best.

It wasn’t until 1913 that males were observed stabbing females through this organ with a horrifying syringe-like penis, then copulating with the wound. Sperm then swim directly to the ovaries through the body cavity. This process has been termed “traumatic insemination."