chelicerae

Chelicerae are the first pair of appendages on the anterior body region of Chelicerata, a group that includes spiders, scorpions, mites, ticks, and horseshoe crabs. Located near the mouth on the prosoma, chelicerae are typically involved in feeding and, in many species, prey capture and defense. They are one of the defining features of chelicerates, distinguishing them from other arthropod groups.

The morphology of chelicerae varies across Chelicerata. In spiders, each chelicera consists of a short basal segment and a long, movable distal segment that forms a hollow fang. The fangs are connected to venom glands in the prosoma, enabling venom delivery to immobilize prey. In scorpions, the chelicerae are usually small, stout, and blade-like, used to macerate food rather than inject venom. In horseshoe crabs and many mites and ticks, chelicerae are adapted to manipulate or cut food and can be less conspicuous than the fang-like chelicerae of spiders. Some mites have highly specialized, needle-like chelicerae for piercing plant or animal tissues.

Functionally, chelicerae serve to seize, pierce, tear, or macerate prey and, in certain groups, to deliver venom or assist in defense. They operate in concert with other mouthparts and, in spiders, work alongside pedipalps and cheliceral glands to process food. Evolutionarily, chelicerae are an early and enduring adaptation that has diversified extensively to meet the feeding and ecological needs of diverse chelicerate lineages.