CLASS III. ARACHNIDA: ORDER 1. DIMEROSOMATA. 
601 
The most remarkable organs perceptible on the abdomen of spiders are the sinnnerets, 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. Tliese 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 speedil}^ hardens on exposure to the air. 
The spider usually commences its thread by applying the spin- 
nerets to some fixed object; to this the glutinous secretion at- 
taches itself, when the movements of the creature are sufiicient 
to draw out the materials necessary for the continuation of the 
spiKNERETs OF A spiDEK MAGNIFIED, thread. Tlic hind-fcct 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 wdiich 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 Gaeden Spider, Ejoeira diadema, 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 sufiicient even to cap- 
ture small birds. Other species, such as the Common House-Spider, Aranea domestica, 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 Avhich a few species carry about with them. Attempts have been made to 
employ this silk, which difi"ers considerably in its texture from that of w^hich 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 
