New science book

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 dont 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.

Walt Whitman:

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.

16 Comments

  1. Posted March 16, 2010 at 7:41 am | Permalink

    The a-r-thropic principle proves the existence of Spiderman.

  2. newenglandbob
    Posted March 16, 2010 at 7:43 am | Permalink

    “Come fly with me” has a different meaning here.

  3. John Blase
    Posted March 16, 2010 at 8:09 am | Permalink

    Having a background in engineering mostly in applied fuid mechanics and thermodynamics I found this piece to be exceptionally interesting. I ask the following question as a complete rationalist ond one who accepts the scientific method as being the most reasonable approacht to understanding nature. I would direct the question to either Dr. Coyne or others with a background in evolutionary biology. What would your speculation (or hypothisis)be for what natural selection forces that might have resulted in this particular adaptation for these spiders?

    Thank you,
    John Blase

    • whyevolutionistrue
      Posted March 16, 2010 at 8:17 am | Permalink

      The conventional explanation, which I think is quite good, is that it’s often adaptive to disperse if, by staying in the neighborhood where you were born, you might suffer a lot of competition with other individuals. This is why plants, for example, have highly sophisticated adaptations for moving their seeds away from the parent. These adaptations can be aerial (wings on maple seeds) or involving animal dispersal (seeds in tasty fruits, or hooks to attach to animal fur). The plant equivalent of a ballooning spider is the dandelion seed, that has its own “silk” to waft it away from the (asexual) parent.

      Such dispersal may often be adaptive for animals, too, especially for a brood of spiders that contain hundreds of individuals who need to get away from each other!

    • newenglandbob
      Posted March 16, 2010 at 8:17 am | Permalink

      Good question, John. It is unlikely they do it for recreation.

  4. Posted March 16, 2010 at 8:13 am | Permalink

    It’s amazing that there is an unseen canopy above our heads teeming with arthropods — at least in the warmer weather. Swifts gorge endlessly on the wing, though we seldom see their prey.

    • Spirula
      Posted March 16, 2010 at 9:24 am | Permalink

      And the massive swarms of insectivorous bats you can see in the SW USA tells you that these huge numbers are maintained pretty much around the clock during the warm months.

      (I think they drop briefly during shift change (dawn/dusk).)

  5. Draken
    Posted March 16, 2010 at 8:16 am | Permalink

    So they take off deliberately, and they can control their descent- but do they have any idea where or when to land? Is it temperature, colour of the ground beneath them, some ancient instinct or dumb luck? (Or, as glider flyers will recognise, simple lack of thermals?)

    • Spirula
      Posted March 16, 2010 at 9:24 am | Permalink

      It’s called “intelligent falling”.

  6. Zoea
    Posted March 16, 2010 at 8:34 am | Permalink

    Darwin commented on the “gossamer spider” in The Voyage of the Beagle.

  7. hempenstein
    Posted March 16, 2010 at 10:14 am | Permalink

    One further reason to be in awe of the tensile strength of spider fibroin, which has not gone unnoticed both at the high tech:

    and low tech levels:

  8. Notagod
    Posted March 16, 2010 at 1:13 pm | Permalink

    Why did he stress that they are always falling? It would seem to me that if the spiders are lucky or unlucky (as the case may be) to find a strong thermal they could easily get very high, even if launching from a very low elevation. If he was taking his thermal measurements in a moist grassy field, possibly like the one that he was trying to catch the spider in, his results would be less than optimal. Several times he stated that the spiders are always falling, I don’t understand why he says that.

    • Will
      Posted March 16, 2010 at 6:22 pm | Permalink

      It’s because the spiders are denser than the air around them. Even in a strong therma the spiders are still ‘falling’ in comparison to the air they are in, but the air they are in rises faster than the spider is falling, thus they have a net increase in height, even though they are never actually flying.

  9. Posted March 17, 2010 at 3:00 am | Permalink

    With every turn of the wheel of complexity, it becomes increasingly unlikely that all this came about unaided even given billions of years. How wondrous is our God.

    • newenglandbob
      Posted March 17, 2010 at 3:54 am | Permalink

      Not wondrous at all since the thing doesn’t exist except in your head in place of thinking.

      Give us examples of that aid or shut up.

  10. Shelldigger
    Posted March 17, 2010 at 5:59 am | Permalink

    At some point during early fall these spiders make themselves noticable by invading the area where I work. (The Tenessee river) For a week or so they are all over the place. (They could be everywhere, but I see them in huge numbers on the river for some reason) I used to come up from a dive and my boat would be infested with friggin spiders, Id wonder where in the hell they came from. One day I decided to sit back and observe, and these little guys are floating about with their little parachutes, and Id watch them come in for a landing on the boat. After a while they will find a spot, start releasing silk, and then just let go, letting the wind take them away. I learned much later of their high flying attributes. Does anyone know yet of the life cycle of these spiders? Id be real interested to learn what exactly they do at altitude.

    @ Draken, Ive witnessed some spiders trying to make landing on my boat, but miss and land in the water. I thought “fish food” but then they sit atop the water, release silk, and take off again. I can only wonder, if the fall invasion has something to do with mating…I dont know.

    Im also in a good position to observe bird and butterfly migrations. I love my job.


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