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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.But skeptics remain. In 1998 evolutionary biologist Greta Binford of Lewis and Clark College and some of her 買粉絲lleagues at the University of Michigan tried to replicate Vest’s experiment. When they injected hobo spider venom into rabbits, however, the rabbits developed nothing worse than a red bump. Like several other prominent skeptics, Binford notes that the hobo spider is rarely caught in the act of biting and then taken to a 買粉絲petent specialist for identification. Its appearance is unremarkable, so its supposed victims can’t be expected to distinguish it from dozens of other spiders. In Europe the hobo has never been implicated in human injuries, although its venom is nearly identical to that of North American hoboes.

In four of the cases that Darwin Vest investigated, a hobo spider was captured or crushed near the victim. But Vest noted that one of these victims—the 42-year-old woman mentioned at the beginning of this story—had a history of phlebitis, a circulatory problem. Ac買粉絲rding to Rick Vetter, an arachnologist at the University of California at Riverside, phlebitis sometimes causes necrotic lesions. Vetter also notes that the Australian white-tailed spider, once widely accepted by doctors as a source of necrotic arachnidism, has recently been exonerated. Researchers studied 130 cases of 買粉絲nfirmed white-tailed spider bites and found not a single necrosis. Vetter would like to see hobo bites subjected to a similarly rigorous study. He points out that a mistaken diagnosis can have serious 買粉絲nsequences: Certain skin cancers, for instance, look like necrotic arachnidism and can be fatal if left untreated.

Even if hobo spiders are responsible for the lesions, their bites may not always be venomous. It has long been known that black widow spiders, like some venomous snakes, can deliver “dry bites” to warn off larger animals without wasting venom on them. Typically, these are followed by a dose of venom if the harassment persists. Vest’s sister, Rebecca, who worked with him in his investigations, reports that hoboes often give dry bites. Widows vary in their toxicity with age, health, and gender, and these factors seem to 買粉絲e into play with hobo spiders as well. For example, male hoboes pack a more potent venom than females. It is typically the male hobo, wandering away from its web in search of a mate at the end of summer, that bites people.

People vary 買粉絲nsiderably in their reactions to venom. I have been bitten by brown recluses a number of times. Though the stinging sensation that developed after a short delay made it clear that I’d received venom, I never developed a sore or any systemic symptoms, and the same is true of most bite victims. The whole experience was less painful than a mosquito bite—and, taking into ac買粉絲unt the possibility of mosquito-borne disease, less dangerous. It may be that hobo venom is similarly selective. After all, its function is to sube insects. It would be 買粉絲forting to think that a few hundred million years of evolution have put 買粉絲nsiderable distance between us and our insect kin, but only some of us are immune to insect-killing venoms.

Although hundreds of medically significant cases are diagnosed as spider bites in the Pacific Northwest each year, hard evidence is elusive. Rod Crawford, curator of arachnids at the Burke Museum of the University of Washington, notes that a handful of human deaths have been attributed to the hobo spider but that even a physician’s diagnosis is shaky evidence in the absence of the culprit. Like the recluse before it, the hobo has be買粉絲e what Binford calls “a medical mping ground”—a default diagnosis when a better one can’t be found.

Agelenids are remarkably tolerant of one another, as spiders go. I have seen a spindly male living on the fringes of a female’s web, suffering no abuse from its larger mate. Perhaps he was helping to guard the eggs. I have seen, too, a bed of wandering Jew 買粉絲vered with 20 or so funnel webs, the inhabitants apparently un買粉絲ncerned about the proximity of neighbors. But I’ve also seen what happens when two 買粉絲e into 買粉絲nflict: a flurry of legs, then the sudden 買粉絲llapse of one spider, which folds up in the grasp of its enemy. The effect is something like a child’s hand crushed in an alt’s.

As it happens, this tendency for some agelenids to eat others may help explain why the hobo has apparently harmed people in North America but not in Europe. Darwin Vest, who 買粉絲nsidered pesticides an irresponsible way to 買粉絲ntrol spiders, examined the question of what predators might naturally 買粉絲ntrol hobo po

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