At the end of the body are the spinnerets, which will be described in another chapter. There are three pairs of them; but many spiders close them together when not in use, so as to cover up the middle pair. The third pair of spinnerets are often several-jointed, and extend out behind the body like two tails. In front of the spinnerets is a little opening, [Fig. 1], K, which leads to air-tubes that give off branches to different parts of the abdomen. At M, [Fig. 1], are usually two colored bands, or rows of spots, marking the course of muscles attached to the skin at various points along these lines.
[Fig. 4] is the back of the same spider. The head is not separated from the rest of the body, as in insects, but forms, with the thorax, one piece. On the front of the head are eight eyes, Q, which are differently arranged in different spiders. At the back part of the thorax is a groove, P, under which is attached a muscle for moving the sucking-stomach, [Fig. 5], d. From this point radiate shallow grooves, that follow the divisions between the muscles of the legs. On the abdomen are several pairs of dark smooth spots, which mark the ends of muscles extending downward through the abdomen. The markings of this spider are very complicated. The spot on the middle of the front of the abdomen is a very common one, and, in some spiders, extends the whole length of the body. The waved lines on each side are also common, and, in long-bodied spiders, often form two bright-colored stripes, or rows of spots, running nearly straight the whole length of the abdomen.
Fig. 4.
INTESTINE.
[Fig. 5] is a section of the same spider. The mouth is at a b, just under and behind the mandibles, and between the maxillæ. It has an upper, a, and under lip, b, each lined with a horny plate, in the middle of which runs a groove. When the lips are closed, the two grooves form a tube, which leads to the œsophagus, c, and so into the stomach. At the end of the œsophagus is the sucking-stomach. This consists of a flattened tube, to the top of which is attached a muscle, d, connected with the groove in the back; and to the bottom, muscles, f, attached to a tough diaphragm spreading across the thorax, and fastened between the legs on each side at g g. When these muscles contract, the top and bottom of the sucking-stomach are drawn apart, and whatever is in the œsophagus sucked in. By this pumping motion the spider is supposed to take liquid food from the mouth, and drive it backward into the abdomen. Just behind the sucking-stomach, the intestine gives off two branches, e e, which extend forward around the stomach muscle, and meet over the mouth. Each of these branches gives off on the outer side four smaller branches, m m m m, which extend downward,—one in front of each leg,—and unite on the under side of the thorax.
