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Reptiles Reptiles

What is a Hobo Spider?

By S. Mithra

Updated: Jun 04, 2024

The hobo spider has finally claimed its reputation that was taken for many years by the brown recluse spider as the most dangerous arachnid of the Pacific Northwest. Since its introduction to American through the port of Seattle on goods shipped from Europe, this spider has been responsible for countless human bites. The end of the 20th century showed its habitat extending into Colorado, Utah, Idaho, and California.

Tegenaria agrestis originated in Western Europe as the "mat weaver of the field." This is because the hobo spider doesn't weave sticky webs to catch flying insects, but spins funnel-shaped mats near the ground. When insects walk on top of or into the funnel, the hobo spider darts out from its "trick web" hiding place and attacks the prey with a poisonous bite. This method of catching food makes the hobo a very aggressive spider in the wild. But when it adapted to city living in America, and began living in close proximity to houses, it became a danger to people as well.

The hobo spider can be identified as a large, brown spider with swollen sacs at the front (male) and a herringbone V-pattern underneath its abdomen. They are predominantly ground, not climbing, spiders that travel around houses and businesses. Chemical fumigation often just kills the hobo spider's competitors. Sticky traps, while effective indoors, puts people in direct contact with a possibly live specimen. Its difficult to significantly reduce their population through fumigation.

The venom of the hobo spider is so dangerous, it's one of a few arachnids listed on the Center for Disease Control's list of poisons. Even though only 50% of bites inject venom and result in tegenarism, the hobo is responsible for more human bites in Northeast America than any other spider. These bites are rarely fatal. At first, the bite spot might resemble a mosquito bite without the itching. After a day, the bite forms a blister that bursts to reveal an open sore. At this stage, unless the victim seeks medical attention, the sore can widen and deepen and cause much tissue damage. The wound will be very slow to heal, leaving noticeable scars.

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Discussion Comments

By anon292065 — On Sep 18, 2012

Why do US-Americans and Britons always crap their pants with everything has eight legs? Is it another conspiracy theory or something like that the end of world is coming?

Funnel weavers of genus agelenopsis/tegenaria with all their species live in Europe, and there is no report of necrosis apart from a mild reaction requiring just an aspirin or so (if any happened during the last 50 years).

In Greece agelaines are all over the peloponnese peninsula in the grass fields and olives or bush or tegenaria close to homes. There are wolves and trapdoors in the fields and segestrias in cracks and bricks of buildings and old houses, yet no confirmation of necrotic lesions.

In my country, even the knowledge of necrosis is just non existent since recluses are rare. Since hobos and relative funnel weavers were introduced to USA from Europe with no necrosis reports confirmed at all, how are those in the USA confirmed? We are talking about the same spiders, not something else.

Spiders evolved during a period of 500,000,000 years and more than humans. They survived many worldwide catastrophes and still evolved. Or do you think they evolved in the USA, producing such venom with poison that does it in 500 years time since appearing in the west? Scientists confirmed that there are no elements causing necrosis on cells in the lab just like the white tailed spider in Australia. The same test was performed on hobos too.

If some are not convinced, then we have to do more on psychology, phobias and the rest, press, media, tv documentaries. This is not a problem for specialists and of reasonably-thinking people. Even on trustworthy sites there is controversy. As they write this and that on hobos saying they are deadly and then overruling the fact, saying they agree, or the spiders are not such a menace at all. And finally, yes, they are venomous.

By anon270042 — On May 21, 2012

Hobo spiders of the agelenidae family are not a threat. Since they were transferred from Europe to North America, there is no story of necrotic arachnidism in Europe all these years.

In my mother's village, funnel weavers are all over the place and nobody told stories like these. Since the poison of tegenaria agrestis is analyzed and does not contain the same elements as the loxosceles recluse has (the dermonecrotic agent, sphingomyelinase D, which is otherwise found only in a few pathogenic bacteria) then the story is told.

By highlighter — On Nov 03, 2010

@ Chicada- I would have to disagree with you and agree with GenevaMech. The truth is that the hobo spider is from a very common species, and it is almost impossible to positively identify unless it is sent to a lab to be viewed under a microscope. People often confuse them with wolf spiders, brown recluse spiders (which do have necrotic poison), and other spiders of the Tegeneria species. You can't simply look at one and conclusively identify a hobo spider. It also doesn’t help that spiders of the same species are often seen running very fast across a person’s floor during breeding season.

There are about twenty other spiders in the Northwest that build funnel webs and none of them are toxic to people. They are not all close relatives to the hobo spider either, but they can be easily mistaken for one. Hobo spider bites are also very mild, and do not show symptoms for hours. Honestly most bites area probably bites from ticks, bedbugs, fleas, and kissing bugs, all of which can cause necrotic legions (all of which are also native to the area). Furthermore, Researchers at UC Davis have also concluded that the Hobo spider is non-venomous, and their poison is identical to the spiders in Europe.

By chicada — On Nov 03, 2010

@ GenevaMech- Why then do people always see hobo spiders around their homes, and why are there always reports of rotted skin associated with the hobo spiders? I can't see that everyone is bitten by a hob spider is wrong about their bites. Hobo spiders are easy to identify because they leave their funnel webs all over the place. I still think they are poisonous and I am not going to take my chances.

By GenevaMech — On Nov 03, 2010

To be honest, most of the stories around funnel web spiders are myths and false truths likely disseminated by those who are afraid of spiders and the pest control industry. Hard science has concluded almost definitively that there is no risk to necrosis from a hobo spider bite. There is also an ongoing study, which is yet to be published, that will further cement this point of view.

The "Annals of Emergency Medicine", a peer reviewed journal, published a piece in 2004 that reviewed claims of necrotic envenomation by hobo spiders form the Pacific Northwest. The researchers examined the medical literature on Pacific Northwest Hobo spiders and concluded that there had only ever been one case of necrotic lesions from a hobo spider bite, and this was from a person who was already inflicted with a disease that made a person susceptible to necrotic lesions. The unpublished study also concluded that the brown hobo spider from the states has failed to produce a necrotic bite in any controlled lab test, and has venom that is identical to the venom of the European Hobo Spider, which is considered non-venomous in Europe.

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