Today’s New York Times gives a good review to Hugh Raffles’s new book, Insectopedia, an encyclopedia comprising mini-essays about insects. Raffles is, of all things, a professor of anthropology at The New School in New York, and has written extensively on insect/human interactions and tropical nature.
The review mentions one intriguing observation: the presence of tons of insects in the air overhead. My students often wonder, when I’m teaching biogeography, how long-distance migration of insects and spiders takes place, since remote oceanic islands often harbor a lot of endemic arthropods whose ancestors must have come from mainlands. I talk a bit about this in WEIT (which I don‘t assign to my students), but here’s more detail from the review of Raffles’s book:
First, that square mile over Louisiana in “Air.” In 1926, P. A. Glick, a scientist from the federal Division of Cotton Insect Investigations, and colleagues from the Department of Agriculture, among others, counted about 25 million to 36 million insects, including a ballooning spider they found flying at 15,000 feet, “probably the highest elevation at which any specimen has ever been taken.” (A Boeing transatlantic passenger jet flies at an average of 35,000 to 40,000 feet.) We know how the Boeing gets up there, but the spider’s launch is an aeronautical feat unequaled by aerospace engineers. Here’s how Mr. Raffles describes what Mr. Glick observed: the spiders “not only climb up to an exposed site (a twig or a flower, for instance), stand on tiptoe, raise their abdomen, test the atmosphere, throw out silk filaments, and launch themselves into the blue, all free legs spread eagled, but they also use their bodies and their silk to control their descent and the location of their landing.” His own sense of wonder is infectious: “Thirty-six million little animals flying unseen above one square mile of countryside? The heavens opened.”
Here’s a nice video of spider ballooning and the intrepid biophysicist who studies it.
A noiseless patient spider
I mark’d where on a little promontory it stood isolated,
Mark’d how to explore the vacant vast surrounding,
It launch’d forth filament, filament, filament, out of itself,
Ever unreeling them, ever tirelessly speeding them.