There are no recorded human fatalities due to mouse spider bites. When severe envenomation does occur, funnel-web antivenom has been shown to be effective. The tarantulas of the family Theraphosidae are fearsome-looking spiders and a favorite of movies and television. The fangs deliver a weak venom and simultaneously crush the insect. The Sydney Funnel web is a relative with a much more potent neurotoxic venom. Trapdoor spiders, many of which resemble tarantulas but are shinier and less hairy, also have large fangs that deliver painful bites, but have very mild venom. New-world tarantulas—those indigenous to the Americas—have bites that generally pose little threat to humans (other than causing localized pain). The primary defense deployed by these spiders is by means of urticating hairs, which can cause irritant symptoms in humans. Old-world tarantulas, especially those indigenous to Asia, lack urticating hairs and may bite as a defensive mechanism. They are far less docile than new-world tarantulas, and are more likely to bite when provoked. Hobbyists report bites by "Poecilotheria" species, occasionally resulting in hospitalization. Symptoms include localized pain and swelling, exhaustion, moderate to severe muscle cramping, labored breathing and fever, sometimes delayed days after the initial bite. Medical documentation is lacking. "Pterinochilus murinus", "Lampropelma nigerrimum" and "Poecilotheria regalis" are other old world species that are noted for possessing particularly strong venom which tends to cause severe muscle spasms. There are several species of spider (and related arachnids) which have had false historical reputations for being harmful to humans. The Centers for Disease Control blamed the hobo spider in three reports of necrotic bug bites in the Pacific Northwest of the United States between 1988 and 1996. Many brown recluse bites have been reported in the U.S. west coast states (Washington, Oregon, and northern California) where populations of brown recluse spiders have not been found. The hobo spider, "Tegenaria agrestis", may wander away from its web, especially in the fall, and thus come into contact with people. Studies performed by arachnologist Darwin Vest reported that this spider's venom caused significant necrotic effects in laboratory animals. Many agricultural authorities have published the advice that this species is potentially harmful, and medical personnel in the western United States and Canada have been advised to consider hobo spider bites when patients present with necrotic wounds.