Araneae

Araneae is an order of arthropods within the class Arachnida that comprises spiders. They are among the most diverse terrestrial predators, with more than 45,000 described species in about 100 families. Spiders typically have eight legs and two main body segments: the prosoma (cephalothorax) and the opisthosoma (abdomen). They possess chelicerae with venom glands and fangs, and most produce silk from spinnerets at the rear of the abdomen for a variety of uses.

Silk serves many purposes in Araneae. Some species spin webs to catch prey, such as orb-weavers and sheet-web builders, while others use silk to line burrows, wrap prey, construct egg sacs, or create retreat structures. Silk can also aid in dispersal through ballooning in certain juveniles. Not all spiders rely on webs for feeding; many are active hunters that use silk primarily for safety and reproduction.

The order is divided into two major living suborders, Mygalomorphae (tarantulas, trapdoor spiders) and Araneomorphae (the vast majority of species), with Mesothelae comprising a small, ancestral group known mainly from fossils. The fossil record of spiders extends back to the Devonian period, and the lineage has diversified widely across terrestrial ecosystems.

Reproduction in Araneae typically involves sexual mating, with males delivering sperm through specialized pedipalps. Females lay eggs in silk cocoons and may guard or retreat with the offspring after emergence. Behavioral strategies and mating systems vary considerably among families.

Spiders play important ecological roles as predators that help regulate insect populations. While some species can deliver painful bites, serious medical incidents are rare. Araneae contribute to biodiversity and are of ongoing interest in ecology, evolution, and biomaterials research.