SPIDER, Aranea, a Linntean genus, now divided not only into man., genera, but into many families, and constituting a section (araneida) of the class aracisnida, and order pulatonaria. The species are very numerous, and are found in all parts of the world, but most abundantly in tropical countries, which also produce the largest species, some of them capable of making very small birds, and not merely insects, their prey (see BIRD-CATCIFING SPIDER). The cepliillothorax, formed by the combination of the head and thorax into one piece, is covered with a kind of horny buckler, generally of an oval form; the abdomen is attached to it by a short stalk, and is generally soft and tumid. Each of the eight legs consists of seven joints, the last armed with two hooks, which are commonly toothed like a comb. The frontal dams, commonly called do not, however, correspond to the mandibles of insects, and move in an entirely different direction, up and down—are terminated by a sharp movable book, which has near its extremity a small slit for the emission of a fluid secreted in a gland of the previous joint. Tke maxilla; are two in number, and tNetween them is an organ called the tongue, forming part of the external apparatus of the mouth. The maxilla.; are the basal joints of the palpi, which resemble very small legs, and are often terminated in the females by a small hook, but in the males by complicated and curious append ages, characteristic of the different genera and species. Spiders have generally eight' eyes; the relative position of -which varies remarkably in the different families and genera. A few species have only six eyes, and a very small number have only two. The upper surface of the abdomen generally exhibits a number of impressed spots, most conspicuous in those kinds which have a smooth naked skin. The pulmonary orifices are either two or four in number, and are situated near the base of the abdomen. Neat' the anus are several spinnerets, small protuberances, pierced at the extremity with a. multitude of minute orifices, from which threads of extreme tenuity- are produced, these threads combining to form one thread of the web. The substance exudes
from the spinnerets is glutinous, and immediately dries into thread on coming in contact with the air. It is elaborated in reservoirs, which terminate in intestine-like tubes. All spiders have spinnerets, and produce threads, although all do not use them for the same purposes; for they differ very much in their habits: some employ their webs in order to catch their insect prey, while others depend for the capture of their prey on their powers of running and leaping; and some weave for themselves habitations in which they live, while others select holes and crevices as their places of abode. Almost all spiders envelop their eggs in silken cocoons, which some of them tear open when the young are hatched; they are attentive to their young, some carrying them for a time on their back, white some carry the cocoons or egg-cases beneath their breast, and others carry them attached to the extremity of the abdomen. Nearly 2,000 eggs have been found in a single cocoon, and the young, when set free, may be seen swarming over the body of the mother, so as almost to conceal her from view. The female spider is, in many of the species, much larger than the male, and a very remarkable danger attends the amatory approaches of the latter, as, if they are not favorablyreceived, he is not uncom monly killed and eaten on the spot. Spiders are very pugnacious, and in their combats often sustain the loss of limbs; but, like crustaceans, they possess the power of repairing this loss. Like them also, they change their skin frequently during their growth; but they undergo no proper transformation. There is much similarity of form among all the multitude of kinds. Many of them exhibit very brilliant and beautiful colors, among which are sonic of the British species, to be found in fields and moors, although the common house spider (aranea domestica) is of very unattractive appearance.