Pharyngula

Spider Kama Sutra

Category: Organisms • Reproduction • Science
Posted on: March 2, 2006 9:28 AM, by PZ Myers

I've been savoring this lovely used book I picked up a little while ago, The Book of Spiders and Scorpions by Rod Preston-Mafham, and am appreciating more than the fact that it is full of beautiful photography of spiders and lots of general information on arachnid behavior and physiology; it's also true that spiders are awfully sexy beasts. They are playful and romantic and kinky and enthusiastic and ferocious and savage and exotic, and really know how to have a good time. I thought I'd share a few of the pretty pictures and details of the arachnid sex life with the readers of Pharyngula—so if you're mature enough to handle it, exuberant enough to enjoy reading about interesting animals doing fun things, and aren't too squicked out at the idea of closeups of spider genitalia, read on.

First, a little anatomy, and we'll start with the female. Here is the underside of a generic spider.

The detail we're concerned with is the epigyne; that is the entrance to the female reproductive tract, and it's in an unsurprising place, the underside of the belly. Over to the right I've included a nice gynecological closeup of the epigyne of Pholcus phalangioides. Isn't it pretty? Epigynes may vary greatly from species to species, consisting of everything from a simple pit to an elaborate plate with bumps and hooks and latches. One mechanism of ensuring species fidelity is to evolve elaborate intromittent organs and complementary vulvae that fit together in a lock-and-key mechanism.

Another feature of the diagram above and an important character for the chelicerates are the mouthparts. The jaw is labeled, with its fangs and crushing/chomping parts, and next to the jaw is unlabeled, segment appendage, the palps. The palps are sensory and manipulatory mouthparts that have another important function—they are the male sex organ. Male spiders don't have penises, and although they do have reproductive organs in the usual abdominal place, they've secondarily modify their mouthparts to do the actual work of mating.

Here, for instance, is a male of the genus Peucetia. The paired green slabs hanging down from his face are the jaws, while the pair of jointed, bristly structures on either side with complicated twisty bits at the end are his palps, which he is probably fantasizing about introducing into the epigyne of a female.

Going courting for a male takes a little preparation. Those palps are nowhere near his reproductive tract, so what he has to do is spin a tiny scrap of web and ejaculate a bit of semen onto it; he then dips his palps into it and fills a hollow channel in them. That's right, the prelude to spider mating is for the male to charge his face up with sperm. This can actually take quite a while, a half hour to several hours, so it's an important part of the process.

Another important and dangerous step is flagging down a willing female. Spiders often have elaborate courtship rituals, with fancy dancing, wig-wagging palps, and fragrant pheromones, all working to convince the female, who is a ferocious predator, that the male is friendly and conspecific and wouldn't she like a little wink-wink-nudge-nudge instead of or before eating him? I can sympathize. I remember when I first asked my wife-to-be out on a date in high school, and I was as nervous as if there were a worry that she might sink her fangs into my skull, inject my cranium with digestive enzymes, and slurp my brains out like a tasty oatmeal milkshake. With spiders, they might really do that.

Once the female gives the all clear, what next? Here are some suggestions from The Joy of Spider Sex, a book that doesn't exist but should.

Here our happy male is going for the gusto and directly pressing his palps against the epigyne, inserting one after the other and squirting their contents into the happy orange lady. This is effective, but note one awkward characteristic of the position: the male is directly beneath the females jaws. This is also the characteristic position for her meals, and one thing you do not want to do while mating with a spider is remind her of dinner.

Now this is not a problem in many species, in which the female may plan on dining on her paramour afterwards, and in some species, the male will actually spontaneously expire upon completion of the act. Males who plan on having sex more than once, though, may prefer the next position.

Here the male is on top, away from those fearsome jaws, and is curling around her side to reach the epigyne with his long and agile phallic palps. This is much, much safer.

This next position requires some long term evolutionary preparation.

Some spider species have an unusually elaborate cephalothorax; their back is festooned with elaborate cuticular protrusions and bumps and hooks and bristles. In these cases, the female clamps onto some of these bumps, like the pommel of a saddle, and may be distracted or entertained…it's like he has evolved a collection of sex toys on his back to keep her happy while he diddles her backside.

I know, you don't want diagrams, you want to see the real thing. Here's a pair of Evarcha falcata gettin' wild. Look at the expression on her face—you know she's loving this.

Spiders can get a bit kinky, too. This species, Xysticus cristatus, has a solution to the problem of hungry ladies: they practice Japanese rope bondage. The male has wrapped the female in webbing to keep her under control while he dives under her belly to do the deed.

Speaking of arachnid mating and sex toys and bondage (clever segue, eh?), the only sex shop proprietress nicknamed after an arthropod that I know, flea of the most excellent weblog One Good Thing, is having a spot of financial difficulty, as I learned on Bitch, Ph.D.. You can help out by browsing their online store, the Honeysuckle Shop, and picking up a few items for your courtship rituals. Despite being named for an arthropod, I notice that she seems to be marketing to an exclusively mammalian clientele (I wonder what a spider sex shop would be like?^*), but since I suspect almost all of the readers of Pharyngula are probably mammals, too, it might work out. Anyway, take a look. Think like a horny spider.

^*I'm thinking they'd be stocked with palp sharpeners, epigyne wrenches, E-Z-Fast sperm loaders, exotic pheromone waxes, self-adhesive cephalothorax twiddlers, and for the more timid males, a line of tranq rifles.