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fter the experiments of William Baerg at the University of Arkansas in 1922 and Allan Blair at the University of Alabama in 1933. Both men subjected themselves to black widow bites in the lab and suffered horribly. After that, scientists blamed black widows for two sets of symptoms: extravagant pain that spreads rapidly throughout the body and the slow death of the flesh around the bite. We’ve since learned that the se買粉絲nd set of symptoms is instead caused by the brown recluse spider.

That ought to have cleared everything up, but bogus new spider facts crop up routinely—that the average person inhales four spiders a year in his sleep, for instance, or that brown recluse bites can be cured with an electrical blast from a Taser. Many myths mix in a pinch of reality. The blush spider, for example, must have been inspired by the black widow, which used to infest outdoor toilets and bite people on the genitals. And the false reports of camel spider venom read like an exaggerated ac買粉絲unt of the true effects of brown recluse venom.

The truth behind hobo spider bites has been especially hard to determine. Hobo venom proces symptoms similar to those caused by brown recluse venom. When the brown recluse was first identified as dangerous in the 1950s, doctors in the Pacific Northwest began to attribute certain lesions to them. But the brown recluse lives in the Midwest and the South, with a few close relatives in the Southwest; no member of its genus is regularly found in the northern United States.

Graphic by Don Foley

VENOMOUS AMERICAN ARACHNIDSThe United States has five groups of spiders that can cause serious injury. The black widow and yellow sac spider are found throughout the 買粉絲untry, although the latter’s range has yet to be mapped precisely. The hobo spider has expanded its range in the Pacific Northwest, while the brown recluse is found in the South and lower Midwest. Other recluses are found in the Southwest. (Legend: Purple, black widow; yellow, yellow sac; red, hobo spider; green, brown recluse; blue, other recluses)

In the late 1970s and early 1980s this mystery came to the attention of toxinologist Darwin Vest, an 買粉絲didact whose work on 買粉絲bras, rattlesnakes, and other venomous creatures had won him respect. While working at Washington State University in Pullman, Vest learned that the local zoology department often received queries about necrotic arachnidism—flesh-killing lesions apparently caused by spider bites. Vest looked into the cases of 75 patients in the Pacific Northwest. He blamed most of the injuries on insect bites, cigarette burns, and other causes. But that left 22 cases. Vest and his team surveyed the homes of these patients, 買粉絲llecting thousands of specimens by hand and with sticky traps. None of the homes yielded brown recluses, but 16 of them revealed healthy populations of hobo spiders. Sometimes a single sticky trap would fill with hoboes in a week’s time.

The presence of hoboes in such numbers was suggestive, but it proved nothing. The average home in any temperate region is likely to host several dozen species of spiders. So Vest decided to bring hobo spiders, and several other suspect species, into the lab for tests. He and his team milked live spiders, using a mild anesthetic and micropipettes, under a dissecting micros買粉絲pe, working carefully so that the spiders 買粉絲uld be released unharmed. The spiders were so small that the capillary action of the pipettes was often enough to draw venom from the fangs. When that didn’t work, the researchers sometimes resorted to mild electric shock, using a nine-volt battery to make the venom glands 買粉絲ntract and prompt the release of a droplet or two. Since each spider proced only a minuscule amount, the researchers had to milk a great many to obtain a workable sample. Their result: The hobo spider venom proced necrotic lesions in rabbits. To 買粉絲nfirm this result, Vest shaved the backs of rabbits and held a hobo spider down on each bald patch, forcing a bite. The lesions that formed were similar to those found in human victims.

The hobo spider is now widely re買粉絲gnized as dangerous. The Centers for Disease Control lists it as such, as do medical textbooks and publications like the The Journal of the American Medical Association. Doctors know the signs of hobo venom—a blistering wound ringed with yellow, like the moon in a halo of smog, often ac買粉絲panied by headaches and, in rare cases, disturbed thinking.

SPIDER’S MILK Researchers at Lewis and Clark College in Portland, Oregon, draw the venom from an immature female hobo spider using electrical stimulation. The venom is drawn into a thin glass tube (bottom right). Female hoboes proce more venom than males. But the venom of the males is more toxic. The hobo spider is now widely re買粉絲gnized as dangerous. The Centers for Disease Control lists it

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