![]() ![]() Except for a few species of very primitive spiders (family Liphistiidae), the abdomen is not externally segmented. The exception to this rule are the assassin spiders, whose cephalothorax seems to be almost divided into two independent units. Spiders, unlike insects, have only two body segments (tagmata) instead of three: a fused head and thorax (called a cephalothorax or prosoma) and an abdomen (called the opisthosoma). Many larger species' bites may be painful, but will not produce lasting health concerns. Only up to 200 species, however, have bites that can pose health problems to humans. Silk can be used to aid in climbing, form smooth walls for burrows, build egg sacs, wrap prey, and temporarily hold sperm, among other applications.Īll spiders except those in the families Uloboridae and Holarchaeidae, and in the suborder Mesothelae) (together about 350 species) can inject venom to protect themselves or to kill and liquefy prey. Many species use it to trap insects in webs, although there are many species that hunt freely. ![]() The study of spiders is known as arachnology.Īll spiders produce silk, a thin, strong protein strand extruded by the spider from spinnerets most commonly found on the end of the abdomen. They are classified in the order Araneae, one of several orders within the larger class of arachnids, a group which also contains scorpions, whip scorpions, mites, ticks, and opiliones (harvestmen). Spiders are predatory invertebrate animals with two body segments, eight legs, no chewing mouth parts and no wings. ![]()
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