Sex on Six Legs_ Lessons on Life, Love, and Language From the Insect World - Marlene Zuk [8]
Crickets are usually rather secretive animals, with the males staying hidden in burrows or leaf litter while they produce their melodic songs. But here, we kept seeing males out walking around on the surface of the grass, brazen as could be, and what was more, they weren't calling. Since calling is the only way male crickets can attract a mate, and since attracting a mate is a cricket's—any insect's—raison d'être, I was puzzled. What were the silent males doing?
In what has turned out to be the only time in my life that I have impressed my husband, also a biologist, with my scientific acumen, I said to him, "The only place I can remember hearing about crickets doing this is in Texas, where they get these acoustically orienting parasitic flies. But I've never heard of any crickets here getting them. I suppose I should look."
As you can probably guess, the next day I was dissecting the previous night's catch of crickets when a white maggot popped out of the body cavity of one of them, like a ghoulish jack-in-the-box. A little more work established that indeed, the crickets in Hilo—and, as it turned out, on Kauai and Oahu as well—didn't only attract the attention of amorous females when they called. They also risked being discovered by flies that use the chirps in a much more sinister way. Once a female fly locates a calling cricket, she deposits tiny larvae on him. A larva, usually one but sometimes two or even three, burrows inside the cricket's body and starts, ever so slowly, to eat his flesh while he is still alive. First it feeds on his body fat, but eventually, as the fly maggot grows until it occupies the entire body, from head to abdomen, it consumes the male's other organs, so that he is a shell that looks like a cricket but is pulsing inside with fly.
I am interested in this grisly process for many reasons, but mainly because it exquisitely illustrates an evolutionary conflict for the males: it is terribly dangerous to call, because males risk attracting the attention of the flies, but calling is the only way to attract a mate. That week in Hilo got me started on a research program I have continued ever since, trying to discover how evolution has worked out the crickets' dilemma. We work, of course, at night, when most of the locals as well as the tourists are elsewhere, in places that tourists would never think to go, and watch as the drama unfolds in the grass. I have learned a great deal from the crickets, and the whole time I feel as if I am in possession of an enormous secret that no one else in the islands, as they drink mai tais and lie on the beach, has any idea exists.
I am fully aware that from most people's perspectives, that's exactly as it should be, and that knowing about pale sticky maggots bursting Alien-like out of the living bodies of other organisms wouldn't enhance their Hawaiian experience one bit. But for some of us, that sense of being in on a hidden world is exactly why we remain fascinated by insects. Several years into the project, I brought my graduate student Robin to Hawaii to study the crickets, and on her first trip we set out a trap to catch some of the flies, a relatively easy matter because of their single-minded attentiveness to the sound of a cricket. All we had to do was play cricket song through a speaker with a tile placed in front of it; the tile was covered with a sticky substance so the flies couldn't get away once they had been attracted to the song.
We turned on the recording and sat on a bench several yards away. After about twenty minutes I told Robin to go check the tile. She came sprinting back, visibly excited. More than a dozen flies speckled the tile, their wings buzzing in frustration. But Robin wasn't just satisfied at a successful experiment; she was also taken aback. The flies are not insubstantial,