The DysderidÆ are a small family of spiders resembling in their general appearance the DrassidÆ, but differing from them in several important characters. They have only six eyes instead of the usual eight, and they have four breathing holes in the front of the abdomen, two of them leading to the usual lungs and the others to the air-tubes, which in most spiders open just in front of the spinnerets.

Dysdera interrita.—Six eyes close together on the front of the head. Length half an inch, with the abdomen a little longer than the cephalothorax. The coxÆ and patellÆ are unusually long, especially on the front legs, and the tarsi are unusually short (fig. 70). The mandibles are long and inclined forward. The maxillÆ are long, a little widened in the middle and pointed at the ends. The labium is long and narrow, and forked at the end (fig. 72). The skin around the base of the legs is thick and hard, so that the sternum appears to extend between them (fig. 72). There are two tracheal openings just behind the openings of the lungs. The cephalothorax and legs are orange brown, darker toward the front. The abdomen is the same color, but so pale as to be almost white.

Ariadne bicolor.—Six eyes in three pairs, the side pairs separated by their diameter from the middle pair. The length is about a third of an inch, the cephalothorax and abdomen about the same length. The cephalothorax is long and the head wide. The maxillÆ are long and narrow. The sternum is widest opposite the third legs (fig. 74), and ends behind in a blunt point. The first, second, and third legs are directed forward, the first pair longest and stoutest. The tibiÆ of the first and second legs are a little thickened in the middle and have four pairs of spines on the under side, and the metatarsus of the same legs eight pairs. The hinder pairs of spinnerets are very small. The cephalothorax and legs are yellow brown, darker toward the front. The abdomen is purplish brown, darker in the middle and toward the front. In the male the head is more narrowed and the front legs longer. The front metatarsi are curved at the base and have a tooth each side, the inner one farthest from the tibia. The palpal organ is outside the tarsal joint, as it is in the Mygales.