Taxonomy 427 Morphology 431 Life History 432 Behavior And Ecology 432 Public Health Importance 433 Veterinary Importance 445 Prevention And Control 446 References And Further Reading 447

All spiders, except the Symphytognathidae and Ulobori-dae, possess venom glands which are used to subdue captured prey. When threatened, however, spiders will often defend themselves by biting, thereby injecting those same toxins into vertebrate skin. In most cases, the venom produces only mild, localized reactions that do not warrant medical attention. Other spiders have much more potent venoms that can cause severe reactions in bite victims, occasionally resulting in deaths. Only about 60 species of spiders worldwide are considered to have significant medical importance. Among them are only a few genera that are dangerously venomous to humans. Most occur in the Subtropics and Tropics. A few tropical species, however, have extended their ranges into temperate regions, particularly those with Mediterranean-like climates.

Envenomation by spiders is called araneism, after Araneae, the arachnid order to which spiders belong.

MEDICAL AND VETERINARY ENTOMOLOGY Copyright 2002, Elsevier Science (USA). All rights reserved.

Separate names, however, are commonly given to bites or syndromes associated with the more dangerous spider genera, each of which is generally characterized by typical clinical signs and symptoms. Examples include atrax-ism (Atrax spp.), cheiracanthism (Cheiracantbium spp.), latrodectism (Latrodectus spp.), loxoscelism (Loxosceles spp.), phoneutriism (Phoneutria spp.), and tegenariism (Tejuenaria spp.). There also are cases in which individuals develop an abnormal fear of spiders such that the mere sight of one can cause panic or hysteria, a condition called arachnophobia or, more specifically, araneophobia. This should not be confused with the unfortunate disdain that many people have for spiders, often reflecting their upbringing and misconceptions about spiders in general.

For general information on spiders, see Comstock (1948), Gertsch (1979), Foelix (1992, 1996), and Preston-Mafham and Preston-Mafham (1984).

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