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When about to produce a thread the spider presses the spinnerets against some object and forces out from each tube enough of the secretion to adhere to it, when the spinnerets are moved away, drawing the viscid liquid out, which hardens at once into threads for each tube. A band of threads is formed when the spinnerets are kept apart, but when closed together the fine threads unite into one or more large ones. Commonly the spinning is aided by the hinder feet, which guide the thread, keeping it clear of surrounding objects, and even pulling it from the spinnerets.

Spiders are best known and hated as animals that bite. Their biting-apparatus, the mandibles, are located in front of the head. Partly in the basal joints of these organs and partly in the head, the poison-glands are seated, from which is discharged through a tube the venom, which makes spiders so much to be feared. This tube opens at the point of the claw of the mandible. When the apparatus is not in use the claws are closed up against the parts between the rows of teeth; but when the jaws are opened to bite the claws are turned outward, so that their points can be made to penetrate anything that comes between the jaws. The ordinary function of the mandibles is the killing and crushing of insects, so that the soft parts can be eaten by the spider, and in this preparation they are substantially aided by the maxillæ. Spiders will sometimes chew an insect for hours, until it becomes a mere ball of skin, only swallowing such bits as may happen to be sucked in with the blood. Let alone and unmolested, they bite nothing except insects that are useful for food. But when attacked and cornered, all species open their jaws and bite if they can, their ability to do so depending upon their size and the strength of their jaws. Notwithstanding the large number of pimples and stings ascribed to spiders, undoubted cases of their biting the human skin are exceedingly rare, and the stories of death, insanity and lameness from spider-bites are probably all untrue. Many experiments have been made to test the effect of the bites of spiders on animals. Insects succumb most readily to their bites, some sooner than others, but birds, except when bitten by the larger Mygale, recover after the lapse of a few hours. The effect upon man, even when the bite is deep enough to draw blood, is like the pricks of a needle, attended by little or no inflammation or pain. Even in cases where death among insects and birds ensues it is claimed by the authorities, men as eminent as Blackwall, Moggridge and Dufour, that the secretion from spiders’ jaws is not poisonous, but that the animals die, when bitten, from loss of blood and mechanical injury.