In the black widow, the fangs point crosswise, and the poison glands extend back into the cephalothorax. They also crush thier prey with theirchelicerae. Pedipalpi are a pair of appendages that look like small legs. One pedipalp is attached to each side of the spider's mouth, andthey form the sides of the mouth. Each pedipalp has six segments (parts). The segment closest to the body bears a sharp plate with jagged edges. The spider uses this plate to cut and crush its food. In adult male spiders, the last segment of each pedipalp bears a reproductive organ. A spider has 4 pairs of legs, which are attached to its cephalothorax. Each leg has 7 segments. In the black widow,the tip of the last segment has 2 or 3 claws. A pad of hairs called a scopula may surround the claws. The scopula stick to smooth surfaces and helps the spider walk on ceilings and walls. Each leg is also covered with sensitive bristiles that serve as organs of touch and perhaps organs of smell. Some bristles pick up vibrations from the ground or air, or the spider's leg. Others detect chemicals in the environment. When a black widow walks, the first and third leg on one side of its body move with the second and forth leg on the other side. Muscles in the legs make the legs bend at the joints. But spiders have no muscles to extend their legs. The pressure of theblood in their bodies makes their legs extend. If a widow's body does not contain enough fluids, its blood pressure drops. The legs draw up under the body, and the animal cannot walk.Spinnerets are short, finger-like organs with which the spider spins silk. They are attached to the rear of the abdomen. The black widow have 6 spinnerets. The tip of a spinneret is called the spinning field. The surface of each spinning field is covered by as many as a hundred spinning tubes. Through these tubes, liquid silkflows from silk glands in the spider's abdomen to the outside of its body. The silk then hardens into a th...
