The opinion, indeed, is equally improbable with another suggested by Dr. Lister, that the spider can retract her thread within the abdomen, after it has been emitted[1]. De Geer[2] very justly joins Swammerdam in rejecting both of these fancies, which, in our own earlier observations upon spiders, certainly struck us as plausible and true. There can be no doubt, indeed, that the animal has a voluntary power of permitting the material to escape, or stopping it at pleasure, but this is not projectile.
3. "There are many people," says the Abbé de la Pluche, "who believe that the spider flies when they see her pass from branch to branch, and even from one high tree to another; but she transports herself in this manner; and places herself upon the end of a branch, or some projecting body, and there fastens her thread; after which, with her two hind feet, she squeezes her dugs (spinnerets), and presses out one or more threads of two or three ells in length, which she leaves to float in the air till it be fixed to some particular place[3]." Without pretending to have observed this, Swammerdam says, "I can easily comprehend how spiders, without giving themselves any motion, may, by only compressing their spinnerets, force out a thread, which being driven by the wind, may serve to waft them from place to place[4]." Others, proceeding upon a similar notion, give a rather different account of the matter. "The spider," says Bingley, "fixes one end of a thread to the place where she stands, and then with her hind paws draws out several other threads from the nipples, which, being lengthened out and driven by the wind to some neighboring tree or other object, are by their natural clamminess fixed to it[5]."
Observation gives some plausibility to the latter opinion, as the spider always actively uses her legs, though not to draw out the thread, but ascertain whether it has caught upon any object. The notion of her pressing the spinneret with her feet
