Whether the bites of the hobo spider are toxic to people has been a matter of scientific debate, but a new study suggests the spider's venom may be less harmful than many people think.
With black widows and brown recluse spiders, hobo spiders are listed by the Centers for Disease Control and Prevention as one of the three venomous spiders that can be found in the United States, that can be dangerous. In some cases, hobo spider bites have caused necrosis, which is the death of cells or tissue, according to a 1996 report from the CDC.
However, researchers have questioned for years whether there is actually sufficient evidence that hobo spider venom can indeed cause necrotic skin lesions, and how dangerous to humans these spiders really are. Moreover, hobo spiders are considered innocuous in Europe, and previous research comparing the venom of American and European members of the species did not find significant differences between the two. [Creepy, Crawly & Incredible: Photos of Spiders]
"There is a psychological thing about spiders, that people just want to believe that spiders are doing the damage," said study author Richard Vetter, an arachnologist at the University of California, Riverside. People may readily conclude that a spider caused an injury they actually incurred from something else, he said.
Hobo spiders are moderately large, measuring about a quarter-inch to a half-inch (7 to 14 millimeters) in body length, with a 1- to 2-inch (27 to 45 mm) leg span. The brown and grey spiders are native to Europe, and were probably introduced into the Seattle area in the 1920s or early 1930s. They have since spread through the Pacific northwest. The spiders build funnel-shaped webs in dark, moist areas, and are fast runners — moving up to 3 feet (1 meter) per second.
In the new study, Vetter and his colleagues examined 33 reported, verified spider bites that occurred in Oregon over three years. Different spider species perpetrated the bites, with one coming from a hobo spider.
The researchers examined the symptoms of the spider bite victims. Unlike some previous studies on spider bites, the researchers looked only at reports in which people actually caught the spiders that bit them, and submitted the eight-legged beasts as evidence.