Only a few members of the Clubionidae, or sac spiders (Fig. 22.8), pose health concerns. Most are Cheira-canthium species, which as a group occur throughout the Northern Hemisphere. Envenomation usually occurs when they are trapped against the skin after crawling into clothing or footwear or when an individual rolls over onto one while sleeping. The bite typically causes immediate local pain, redness, and formation of a wheal similar to that from the sting of a wasp or bee. In some cases the victim may experience a persistent loss of sensitivity involving the musculature and nerves at the bite site. Tissue surrounding the puncture wound often becomes necrotic,

FIGURE 22.8 Sac spider, Cluhiona obesa (Clubionidae), female. (From Gertsch, 1979.)

forming a small skin lesion. In more severe cases, systemic responses may include mild fever, nausea, and loss of appetite. No deaths have been attributed to spiders in this genus.

Cheiracanthiwrn punctorium is the species most commonly involved in cases of cheiracanthism in Europe. Its bite causes a painful burning sensation and associated swelling, which may persist for several days. Other reported symptoms include chills, general muscular aches, and tenderness of regional lymph glands. Envenomation by C. japonicwm in Japan is similar to that by C. punc-torium but also may involve local petechiae (purplish, hemorrhagic spots on the skin), nausea, vomiting, and, rarely, shock. Reactions to one of the two species found in North America, C. inclusum, are painful but relatively mild compared to C. punctorium and C. japonicum; however, C. mildei has been reported to sometimes cause severe necrosis similar to a recluse spider bite. Several of the Gheiraccmthium species of medical importance are fairly recent introductions from other parts of the world. These include C. mildei, introduced to the United States from Europe; C. mordax, introduced to Hawaii from Australia; and C. diversum, introduced to Hawaii and Fiji from Australia.

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