Class Arachnids

Arachnids are land arthropods: they have no antennae, have 4 pairs of walking legs and 2 pairs of mouthparts, breathe with lungs or tracheae and have separate sexes. The class is divided into the orders spiders, solifuges, scorpions and mites. The cross spider’s body is divided into a cephalothorax and a smooth round abdomen; the cephalothorax carries 4 pairs of simple eyes, chelicerae (with venom glands), sensitive pedipalps and 4 pairs of walking legs. At the end of the abdomen are three pairs of spinnerets: the liquid from them hardens in air into silk. The female weaves a wheel-shaped orb web; when the signal thread vibrates the spider runs out, wraps the prey in silk, kills it with venom and sucks up the tissues dissolved by digestive fluid. Its venom does not affect humans. Breathing: one pair of book lungs and two tufts of tracheae. In autumn the female weaves a silk cocoon and lays eggs in a hidden place; the spiders die in winter, the eggs overwinter and young spiders hatch in spring.