Are Hobo Spiders Actually Dangerous? What Montana Residents Should Know

Hobo spiders can cause painful bites with localized redness and swelling, but current scientific evidence does not conclusively support the earlier claim that their venom causes severe tissue death (necrosis) in humans. Most bites result in mild to moderate local reactions. While they are not considered medically significant in the same category as black widow or brown recluse spiders, hobo spiders should still be treated with caution — especially by individuals with sensitivities or allergies.

What Is a Hobo Spider?

The hobo spider (Eratigena agrestis) is a medium-to-large funnel web spider originally from Europe, introduced to the Pacific Northwest in the 1930s and now firmly established across western Montana. It is one of the most commonly encountered large spiders in Montana homes, particularly in basements, garages, and ground-level rooms during late summer and fall.

Hobo spiders belong to the funnel weaver family, they build flat, sheet-like webs with a funnel or tube retreat at one end, positioned at ground level in dark, sheltered locations. The spider waits inside the funnel for prey to stumble across the web surface.

How Do I Identify a Hobo Spider?

A hobo spider is a medium-to-large brown spider, roughly ¼ to ½ inch in body length with a leg span of up to 2 inches, with chevron-shaped markings on its abdomen and no distinctive color bands on its legs. It is most often found at or below floor level and is a fast runner but a poor climber.

Here's the problem: hobo spiders are genuinely difficult to distinguish from several other similar species without a microscope — including the giant house spider (Eratigena atrica), which is larger, non-venomous, and has actually displaced hobo spiders in many urban areas over the past two decades.

What Does Science Actually Say About Hobo Spider Venom?

The scientific consensus on hobo spider venom has shifted significantly over the past 20 years — and it's worth understanding that shift, because a lot of outdated information still circulates online.

The earlier claim: Research published in the 1980s and 1990s suggested that hobo spider bites could cause necrotic (tissue-killing) lesions similar to brown recluse spider bites — a condition called necrotic arachnidism. This led to the hobo spider being listed as a medically significant species by the CDC.

What more recent research found: Multiple subsequent studies attempting to reproduce these results in controlled conditions were unable to confirm that hobo spider venom causes necrosis. The CDC removed hobo spiders from its list of venomous spiders of medical significance in 2017 based on this evolving evidence.

What is agreed upon today:

• Hobo spider bites can cause immediate pain, redness, and local swelling

• Some individuals report headache and fatigue following bites

• Severe systemic reactions are rare

• The necrotic wound cases previously attributed to hobo spiders in the Pacific Northwest are now largely attributed to other causes — including misidentification and pre-existing skin conditions

The bottom line: Hobo spiders are not harmless, a bite is unpleasant and can cause real discomfort. But they are not the necrosis-causing menace they were once believed to be. The bigger concern for most Montana households is population management, not individual bite severity.

When Are Hobo Spiders Most Active in Montana?

Hobo spiders are most active, and most frequently encountered indoors, from August through October. This is mating season for hobo spiders, when males abandon their webs and roam in search of females. During this period, the number of spiders encountered at floor level in Montana homes increases dramatically. Females remain in their webs year-round.

Why you see them more in fall:

• Male hobo spiders travel up to several hundred yards searching for a mate

• As outdoor temperatures drop, spiders move toward warm structures

• Roaming males are more visible than stationary web-dwelling females

• August through September represents peak encounter risk in Montana

  
  

Where Do Hobo Spiders Hide in Your Home?

Hobo spiders are almost exclusively ground-level dwellers, they cannot climb smooth vertical surfaces. They are most commonly found in:

• Basements and crawl spaces — dark, humid, sheltered, ideal funnel web habitat

• Window wells — a classic accumulation site; the well walls trap spiders that enter

• Under furniture — particularly in ground-floor rooms and basements

• Behind stored items — boxes, equipment, and clutter on basement or garage floors

• In gaps along foundation walls — where wall meets floor in unfinished spaces
  

If you're finding spiders consistently in your bedroom or upper floors, they are almost certainly not hobo spiders, a more likely candidate at upper levels is the giant house spider or a cellar spider (Pholcus spp.).

What Should I Do If I Find a Hobo Spider?

Do not attempt to handle it. Even if hobo spider venom is less severe than once believed, a bite is still painful and can cause a localized reaction. Use a glass and piece of cardboard to capture it if you want it removed from the immediate area.

Do not crush it on a surface. This leaves a stain and can release an odor that attracts other spiders.

If bitten:

1. Clean the bite site immediately with soap and water

2. Apply a cold compress to reduce swelling

3. Take an antihistamine if local reaction is significant

4. Monitor for worsening symptoms — increasing pain, spreading redness, fever, or systemic effects

5. Seek medical attention if symptoms worsen over 24–48 hours or if the patient is a child, elderly, or immunocompromised
   

For recurring spider problems in your home: The presence of spiders, including hobo spiders, indicates an underlying insect population providing food. Reducing the insect pressure in your home reduces spider pressure. Montana Pest Solutions addresses both the spider population and the underlying insect activity driving it.

How Do I Keep Hobo Spiders Out of My Home?

The most effective hobo spider prevention combines perimeter treatment, physical exclusion, and reduction of harborage sites.

Seven proven prevention steps:

1. Move firewood away from the house — Woodpiles are prime hobo spider habitat; keep them at least 20 feet from the foundation

2. Declutter basements and garages — Boxes and stored items on the floor are ideal web sites; get them off the floor and organized

3. Install window well covers — Plastic covers over window wells prevent spiders (and other pests) from collecting there

4. Seal ground-level gaps — Caulk around window wells, utility entry points, foundation cracks, and gaps where pipes enter the structure

5. Reduce exterior lighting — Lights attract insects, insects attract spiders; switch to yellow "bug lights" on exterior fixtures

6. Shake out shoes and clothing — Particularly in late summer, check footwear left on the floor and clothing stored in ground-level areas

7. Schedule a perimeter treatment — Professional residual insecticide applied to the exterior foundation and interior baseboards in late summer significantly reduces hobo spider entry

Montana Pest Solutions provides spider control and perimeter treatments across Missoula, the Bitterroot Valley, and surrounding communities. If spider season in your home is getting out of hand, we're one call away.

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