What this shows: the six spiders most often found in and around Treasure Valley homes, compared on the features you can actually check: size, markings, web style, and where each one turns up. Danger levels follow current entomology guidance rather than reputation, which is why the famous hobo spider sits at low and the quiet black widow sits alone at the top.
The chart
| Spider | Size | Look for | Web or hunter | Where you find it | Honest danger |
|---|---|---|---|---|---|
| Hobo spider | Body 1/4 to 1/2 in, legs span to about 1.5 in | Muted brown, subtle herringbone pattern down the abdomen, plain legs without dark bands | Low funnel web; mature males wander indoors Aug-Oct | Rock beds, window wells, foundation lines, garages, basement floors | Low Dropped from CDC's list of spiders of medical concern |
| Funnel weavers, incl. giant house spider | Body to 3/4 in, legs span to 3 in | Brown with two dark stripes on the front section; many have banded legs | Sheet web with a funnel retreat; waits at the mouth | Lawns, shrubs, window wells, garages, crawl spaces | Low Startling size, no medical significance |
| Wolf spider | Body 1/4 to 1 in, stocky | Gray to brown and hairy, with two large forward facing eyes that shine in a flashlight beam | No web; a ground hunter that chases prey down | Lawns and rock by day, floors and garages in fall, often under doors | Low Rare bite, comparable to a bee sting |
| Western black widow | Body to 1/2 in, legs span to 1.5 in | Glossy black with a red hourglass on the underside of the abdomen | Strong, messy, three dimensional web built low and left in place | Garages, meter boxes, woodpiles, sheds, window wells, under patio furniture | Medically significant The one Idaho spider whose bite warrants medical attention |
| Yellow sac spider | Body 1/4 to 3/8 in | Pale yellow to cream with darker mouthparts | No snare; hunts walls and ceilings at night, rests in a small silk sac by day | Wall and ceiling corners, behind frames, blinds, and headboards | Mild but real The likeliest true biter, a painful welt that heals on its own |
| Cellar spider | Body to 1/3 in, thread thin legs to 2 in | Tan to gray, tiny body, extremely long legs | Loose, tangled web it vibrates rapidly when disturbed | Basements, crawl spaces, garage and closet ceiling corners | Harmless The deadly venom story is an urban legend |
Three checks that identify most spiders
First, the web. Funnel shaped sheet webs in rock beds and window wells mean the agelenid family: hobo, giant house, or grass spider. A strong, disorganized tangle low in an undisturbed corner points to a black widow. A wispy tangle on a basement ceiling is a cellar spider. No web at all means a hunter: a wolf spider on the floor, a yellow sac spider on a wall or ceiling at night.
Second, the location and the hour. Fall evenings on open floor almost always mean wandering males, hobos and wolf spiders on mating patrol, which is the September pattern covered in the September spider surge. Third, the specific marks: the hourglass underneath a widow, the eye shine of a wolf spider, the herringbone abdomen of a hobo. Flip nothing by hand; use a flashlight and a photo.
The one to take seriously
The western black widow is the only spider on this chart with venom that matters medically, and it is also the easiest to avoid: it stays in its web, in clutter nobody moves. Flashlight check the classic zones before reaching in: garage corners, meter boxes, woodpiles, under patio furniture. Bites are rare and essentially never fatal with modern care, but they deserve a doctor's call. Clearing widow habitat is a standard part of our spider control service.
Found something on this chart you would rather not share a garage with?
Get a Free Quote →The one that is not here: brown recluse
The spider people most often think they found does not make the chart on purpose. University extension records show no established brown recluse populations in Idaho. Nearly every valley "recluse" photo turns out to be a hobo, another funnel weaver, or a wolf spider. A real recluse has six eyes arranged in three pairs, a violin mark on the front section, and uniformly colored legs, and it lives a long way from here.
Where this chart comes from
The features and danger levels above are synthesized from university extension spider guides for Idaho and the Intermountain West and from current medical entomology, including the research that retired the hobo spider's scary reputation. For the narrative version, with habits, myths, and the valley's spider year, read spiders in Idaho.
Spider identification questions
How can I tell a hobo spider from a brown recluse?
Idaho makes this one easy: university extension records show no established brown recluse populations in the state, so a brown spider here is almost certainly a hobo, another funnel weaver, or a wolf spider. If you want the marks anyway, a recluse has six eyes in three pairs and a violin shape on its front section, while a hobo has eight eyes and a herringbone patterned abdomen.
What is the fastest way to identify an Idaho spider?
Start with the web. A funnel shaped web means the agelenid family: hobo, giant house, or grass spider. A strong, tangled web low in clutter says widow, so check for the hourglass underneath. A loose, flimsy tangle on a basement ceiling says cellar spider. No web at all points to a wolf spider on the floor or a yellow sac spider up on walls at night.
Which of these six spiders actually bite people?
Rarely any of them, but two have a real record. The yellow sac spider bites when trapped against skin and leaves a painful welt that heals on its own. The black widow bites when pressed or disturbed in its web, and that bite warrants medical attention. Medical guidance attributes most mystery bumps and welts to causes other than spiders entirely.
Is the big funnel weaver in my window well a hobo?
Maybe, but the group matters more than the species. Hobos, giant house spiders, and grass spiders share the same funnel web style and are genuinely hard to separate without magnification. None of them are medically significant, and giant house spiders actually compete with hobos. A large one with striped front and clearly banded legs is probably not a hobo.
Do I need to know the exact species before calling for treatment?
No. Identification changes urgency, not method. A widow find means clearing clutter zones carefully and checking for more, while everything else on this chart is routine. A professional spider service treats the whole group at once: webs, egg sacs, entry gaps, and the insect prey that feeds them. An uncertain ID never blocks the fix.