What are a spider's venom-injecting mouthparts called?

A spider’s venom-injecting mouthparts are called chelicerae. Each chelicera consists of a basal segment and a terminal fang, with the fang positioned to pierce prey and deliver venom in most spiders.

The chelicerae are attached to the front body section, called the cephalothorax or prosoma. They are a defining feature of chelicerates, the arthropod group that includes spiders, scorpions, horseshoe crabs, and sea spiders. In spiders, the chelicerae have evolved into compact fang-bearing structures rather than the large crushing jaws associated with many insects and crustaceans.

The fangs are not the entire mouth. Spiders also have pedipalps, which sit behind the chelicerae and help manipulate food; in mature males, the pedipalps are modified for transferring sperm. Spiders generally cannot chew solid food in the mammal-like sense. They use venom and digestive enzymes to subdue prey and begin breaking tissues down, then draw in liquid food through the mouth. Mandibles and maxillae are common terms for mouthparts in other arthropod groups, but they are not the canonical answer here.