Last week, the journal The Science of Nature published an exciting finding: An extinct cousin of the daddy longlegs, Halitherses grimaldii, was found in Burma and fossilized in amber with its long, spindly penis on full display. According to the National Geographic, the creature's fossilized penis is one best preserved examples ever discovered. This aroused the interests of the scientific community and laymen alike: Who knew that arachnids could have mammal-like erections? And really, who knows anything about spider genitals at all?
I certainly didn't, until I talked to Dr. Brian Brown, the curator of the entomology section at the Natural History Museum of Los Angeles County, who first clarified that daddy longlegs, or harvestmen, aren't actually spiders, though they're close relatives. And one of the aspects that differentiates harvestmen from spiders is that they have dicks, in the traditional sense.
"When you think about insects and arachnids and so-on, there's an incredible variety of male genitalia for getting the sperm into the female reproductive system," Brown tells me over the phone. "Some of the devices are really elaborate, and then there's some that look superficially like human genitalia, like the daddy longlegs in the fossil."
In this way, daddy longleg sex looks a little more familiar than spider sex—and it's lot more straightforward. It's well known that female spiders have, well, misandrist tendencies: When a male spider attempts to mate with a female, he has to first avoid getting eaten. "Spider males have to mate with their females, which are extremely predatory," Brown says. "For this, spider males have special structures called pedipalps under their legs. What they do is reach down with their pedipalps and charge them up with sperm. When they go to mate with the female spider they sort of gingerly extend their pedipalps toward her, without having to go for genitalia-to-genitalia contact."
Another measure spiders employ for avoiding death is seduction. Because female insects and arthropods can mate with many males, store the sperm in a structure called the spermatheca, and "choose" which sperm deposit they want to use to fertilize their eggs, males have to develop ways to prove their sperm is the best. A species of spider in Madagascar does this by performing oral sex on female mates to curry favor. "The thing with insects and other types of arthropods is that they often can mate with more than one mate, and the females can control the sperm in ways that human females can't," Brown says. "So the males have it a lot harder than human males, for instance. They not only have to get the females to mate with them, they have to get the females to use their sperm."
Harvestmen, Brown speculates, have their own method of making sure their sperm leads to successful reproduction that lies in the heart-shaped tip of the penis. "I can't say for sure, but [the shape] probably has something to do with manipulating the sperm in the female spermatheca, where the females store the sperm. It could be used to scoop out any sperm that's there from another male before it deposits its own sperm."
And really, who knows anything about spider genitals at all?
The characteristics of this particular harvestman's penis should be typical throughout other members of the species, Brown notes. "Generally, the genitalia size doesn't vary that much within arthropods because the males and the females have to fit together in a certain way. Arthropod structures are hardened; they're made out of exoskeleton, like the rest of the body. There's not a lot of give, so the genital structure has to be precise," he says.
Though Brown also tells me that the now-infamously erect harvestman might not even have an erection, as first reported by the National Geographic. Troublingly, I learned, the genitals on a male arachnid are always extended outside their bodies. "Arachnids don't necessarily have erections like mammals do," he says when I asked what type of scenario a young, virile harvestman would have to put himself in to die so... happily. "That structure is [made of] hardened, sclerotized material. It's always going to look like that."
"The other story," referring to a romantic narrative in which the intrepid harvestman died atop a tree just as he was about to copulate with a lover, "sounds better," he admits.