Spiders are not insects. They are close relatives of ticks, mites and scorpions, which all belong in the group called arachnids. Unlike insects, which have three main body sections and six legs, spiders have two body sections and eight legs. The eyes, mouthparts and legs are found on the front section of the body, known as the cephalothorax. The second section, the abdomen, bears the openings for breathing, the digestive and reproductive systems, and the external organs used for spinning silk or webbing.
Female spiders wrap their eggs in a silken spun sac.
Some species carry this egg sac, while others deposit it somewhere within their nest. Encounters between people and spiders are usually accidental and bites are a defensive response by the spider when its web or nest is disturbed. The venom is stored in glands that empty into the spiders fangs' or chelicerae. For the most part, spiders bites are of no consequence. However, just as bee and wasp stings may trigger allergic reactions in some people, the same can be true for spider bites.