DOWN THERE (Part 1): Making Sense of Amazing Genitalia

DOWN THERE (PART 2): Pull Out The Genitalia & Everything Becomes Clear

A flea penis. (Photo: © Power & Syred, reprinted by permission)

At 10 p.m. on an evening late in Spring, in the hazy orange light of a convenience store parking lot, fat brown Junebugs buzz through the air looking for love.  A young biologist watches closely till she spots a happy couple retreat to the low branches of a nearby tree.  Junebug sex typically lasts two hours, perhaps because fitting all those parts together can be complicated.  After a while, the biologist takes two cans of refrigerant from her bag, holds them up on either side of the mating pair, and starts to spray.  The male, seated behind, stops moving, and white lines of frost advance across their firm, young bodies.  “Poor babies!” an undergraduate assistant cries out, and then the biologist drops the pair into a jar of alcohol.  Next day in the lab, she will slice them in two to examine how all the little indentations and protuberances of male and female genitalia line up for a “super-tight fit, like a Chinese finger trap.”

Biologists have always been a little more interested in genitalia than the rest of us.  It’s not because they are sexually obsessed, any more than the rest of us.  What the British call the “naughty bits” have typically been the single best answer to one of the great challenges in biological classification:  Many small creatures, particularly insects, look alike, at least outwardly.  Even taxonomists who have devoted their careers to biological classification often cannot tell two species apart.  But when “you pull out the genitalia,” as the Junebug biologist puts it, everything suddenly becomes clear.  Even closely-related species often turn out to be radically different.

Nobody knew why genitalia would vary so much from one species to the next.  But for the past 250 years, back to the time of Linnaeus, experts in different animal groups have been using genitalia as a key feature for identifying species.  These experts typically focus on male genitalia, partly because they’re easier to examine. It’s not so easy to notice if the female of the species evolves a sensitive cluster of nerves in some corner of the genitalia.  But the hard ridge or bump the male subsequently evolves to stimulate that nerve cluster is a lot more obvious.  Not only are nerves more difficult to see, but soft tissue tends to dissolve more readily in the fluids used during a dissection.  Male genitalia are also where most of the bizarre diversity seems to occur, though, again, past scientists seem not to have thought much about why this should be so. 

A lot of people preferred not to think about genitalia at all . Darwin’s own daughter Henrietta was a classic case of how the topic could cause some people to become utterly unhinged.  According to Period Piece, a family history by Darwin’s granddaughter Gwen Raverat, “Aunt Etty” used to make outings to eradicate the stinkhorn fungus, a rank-smelling toadstool whose scientific name, Phallus impudicus, or “shameless penis,” reflects its appearance. 

“Armed with a basket and a pointed stick, and wearing a special hunting cloak and gloves, [Aunt Etty] would sniff her way round the wood, pausing here and there, her nostrils twitching, when she caught a whiff of her prey; then at last, with a deadly pounce, she would fall upon her victim, and poke his putrid carcase into her basket.  At the end of the day’s sport, the catch was brought back and burnt in the deepest secrecy on the drawing-room fire, with the door locked; because of the morals of the maids.”  But clearly Aunt Etty was off her nut, perhaps traumatized by early exposure to barnacles.

Most modern biologists regard the study of genitalia as no more emotionally loaded than the study of antennae.  Developing a photographic memory for minute variations in, say, moth penises is simply part of the job, though it can be an exceedingly tedious part, given that these penises may be only a fraction of an inch in total length.  It’s a measure of how determined they can be that, in 1998, one specialist invented a device for inflating insect penises and permanently hardening them for detailed examination.  He called it “The Phalloblaster” and it retailed to like-minded biologists for $3000. 

The inventor was not, as it happens, off his nut.  He wanted to identify moth species that are major agricultural pests.  Targeting the right moths, rather than an identical-looking kindred species, could, he said, dramatically reduce crop damage and hunger in India.  But it is probably the fate of anyone who studies genitalia to be misunderstood.  One Australian publication greeted his work with the headline, “Moths’ penises could help feed India.”