Chelicerae
From Free net encyclopedia
The Chelicerae are mouth parts of the Chelicerata, a subphylum that includes arachnids, merostomata (horseshoe crabs), and pycnogonids (sea spiders).
Spider chelicerae
The chelicerae consist of a base segment that articulates with the cephalothorax and a fang portion that articulates with the base segment. Think of a two-segment finger, the outer segment of which consists of a hollow fang. Except for two very small families of spiders, they all have venom that is injected into their prey through openings in the tips of their fangs. The glands that produce this poison are located in the two segments of the chelicerae, and, in most spiders, extend beyond the chelicerae and into the cephalothorax. Chelicerae are also found in related creatures such as the scorpions.
Image:Spider chelicerae.png
This overhead drawing shows the chelicerae in black, the surface of the cephalothorax in brown, the spiders legs in reddish brown, and the poison glands and surrounding muscle tissue (used to squeeze out the venom) in green.The fang portion of the right chelicerae can be seen projecting into the space between the two chelicerae.
Image:Spider chelicerae2.png
The second drawing shows a side view of the cephalothorax of the spider in brown (with the legs removed) and the two portions of the chelicera.
