Why do spiders have venom even if they are not snakes?

Spider venom is delivered through fangs and is primarily a feeding tool. Because spiders cannot chew like mammals, venom helps subdue insects and other prey and starts breaking down tissues for later consumption. In many species, the venom is tailored to target the nervous systems of small arthropods rather than large animals. Only a small number of spider species are medically significant to humans, but the evolutionary role of venom is central to spider ecology. The Australian redback and the Brazilian wandering spider are among the better-known medically important spiders.