CLASS III. ARACHNIDA: ORDER 1. 1)1 M EROSOM AT A. 



601 



SPINNEEETS OF A SPIDEE MAGNIFIED. 



The most remarkable organs perceptible on the abdomen of spiders are the spinnerets, by 

 means of which they spin their curious and often beautiful webs, which have attracted the atten- 

 tion and excited the admiration of mankind in all ages. These spinnerets are little teat-like 

 organs, placed close to the extremity of the abdomen, on its lower surface. They are sometimes 



four, sometimes six in number, and may usually be recognized 

 by the naked eye. Each of them bears at its apex a multitude 

 of minute tubes, of which as many as a thousand are present in 

 some species ; so that the delicate thread by which these crea- 

 tures suspend themselves in the air must frequently be composed 

 of at least four thousand slender filaments. The substance of 

 which the threads are composed is secreted by glandular organs, 

 situated in the abdomen, close to the base of the spinnerets. It 

 is a viscid fluid, which speedily hardens on exposure to the air. 

 The spider usually commences its thread by applying the spin- 

 nerets to some fixed object ; to this the ghitinous secretion at- 

 taches itself, when the movements of the creature are sufiicient 

 to draw out the materials necessary for the continuation of the 

 thread. The hind-feet are always applied to the thread at a 

 short distance from the spinnerets, probably in order to bring 

 the numerous filaments into contact before their hardening has proceeded too far to allow of 

 their adhesion. This power of spinning threads is of the greatest importance to all these ani- 

 mals, as it not only serves many of them for the construction of dwellings, and of nets for the 

 capture of prey, but appears to be constantly employed in securing them from falls while in mo- 

 tion, or in descending in a direct line from an elevated position to some object below them. 

 Many of them have the faculty of emitting threads, one end of which floats freely in the air 

 until it meets with some object to which it adheres. By this means spiders often form natural 

 bridges, by which they can pass over brooks and ditches. Some species avail themselves of the 

 same power to take long flights in the air, where they often attain great altitudes. Those spi- 

 ders whose instinct prompts them to employ their spinning powers in regular weaving opera- 

 tions, manifest this in various ways. 



Some, of which the Common Garden Spider, Epeira dladeina, is an excellent example, con- 

 struct a beautiful net, composed of stout radiating lines, intersected at tolerably regular intervals 

 by circular filaments. It appears that the latter are beset by an immense number of viscid 

 globules, which doubtless assist greatly in entangling any insect that is so unfortunate as to 

 come in contact with the web of the destroyer. The mode in which the creature forms this ele- 

 gant structure, its readiness to rush out of its concealment the moment some hapless fly has be- 

 come entangled in its meshes, the rapidity with which it shrouds its victim in a silken coat, and 

 the care with which it repairs any damage done to its net, are all exceedingly curious and inter- 

 esting points in its natural history. 



The nets of some of the large tropical spiders are said to be of strength sufficient even to cap- 

 ture small birds. Other species, such as the Common House-Spider, Aranea domcstica, weave 

 a close, cloth-like web, usually placed in obscure corners ; this is furnished with a sort of funnel- 

 shaped cell, within which the spider lies in wait for his prey. Others again employ their silk 

 merely to line the holes and crevices which form their ordinary places of abode ; and some of 

 these exhibit great ingenuity in the construction of their nests. Another purpose to which this 

 secretion is applied by all spiders, is the formation of little silky cases or cocoons for the recep- 

 tion of the eggs, and which a few species carry about with them. Attempts have been made to 

 employ this silk, which diff"ers considerably in its texture from that of which the nets are con- 

 structed, for industrial purposes, but hitherto with very little success. 



The spiders are all predaceous animals, and generally of an exceedingly fierce and sanguinary 

 disposition. They prey with avidity upon insects and other articulated animals of smaller size 

 than themselves ; but, unless in self-defense, they do not appear to turn their weapons against 

 the higher animals. They are divided into several families. 

 Vol. II.— 76 



