Spider Season in Iowa: Brown Recluses & Lookalikes

Q: Why are there so many spiders in my house in Iowa right now?

Spiders start turning up indoors around August 15, the wandering peaks between September 1 and October 15, and it fades by November 10. Those are male house spiders and funnel weavers looking for mates, plus spring hatched spiders that have finally grown large enough to notice. The widow record in Iowa peaks in the same stretch, because females are at full size.

Q: Are there joro spiders in Iowa?

No verified joro spider record exists in Iowa yet. The species has spread outward from north Georgia since 2014 and first records keep appearing in new states, so the year by year series on the national page is the thing to watch. A large yellow and black spider on a web here is almost always a yellow garden spider, which is native and of no medical concern.

Q: Are there black widows in Iowa?

No widow species reaches the record threshold in Iowa. The spiders of medical concern here are recluses, and the glossy black spider in a low web is almost always a false widow or a common house spider, both of no medical concern.

Q: Are there brown recluse spiders in Iowa?

Yes. Iowa has the brown recluse (13 records). The brown recluse lives indoors in undisturbed spaces: stored boxes, closets, attics, behind furniture, and inside clothing or bedding left on the floor. Shaking out clothes and shoes, and keeping beds off the wall, removes most of the risk.

Q: Where do widows and recluses live in Iowa?

Farm barns, machine sheds and woodpiles. Older houses, closets and stored boxes in the southern counties. Basements and garages across the Des Moines and Cedar Rapids suburbs. The verified record clusters where people live and look, so Southern Iowa carries the most records and roadless country the fewest.

The list

The one widow or recluse species recorded in Iowa

Every species below has verified, photograph backed records in Iowa. The counts come from iNaturalist and measure how often people find and photograph each spider, never how many there are: a species of packrat nests will always look rarer than one of garages.

Species	Group	Verified records	What to look for
Brown recluse Loxosceles reclusa	Recluse	13	Uniform tan to brown, six eyes in three pairs, a darker violin shape on the front body segment, and legs with no bands and no spines. Lives in undisturbed indoor spaces: stored boxes, closets, attics, behind furniture.

Below the record threshold, documented by the state’s extension or health service.

Brown recluse (13 records): Iowa State University Extension and Outreach reports the brown recluse as present in Iowa, established mainly in the southern counties and found indoors.

A brown recluse spider on a plain pale surface, uniform tan with long unbanded legs and a darker violin shaped mark on the front body segment — A brown recluse: uniform tan, legs with no bands or spines, six eyes in three pairs, and a darker violin on the front segment. It lives in undisturbed indoor spaces and wanders at night. “Brown-recluse-2”, Br-recluse-guy, Public domain

A barn funnel weaver on a white ceiling seen from above, brown with two dark stripes on the front body segment and a mottled abdomen, its legs spread wide — For contrast, the barn funnel weaver that makes up most of the autumn indoor record: striped front segment, mottled abdomen, a sheet web with a funnel. Of no medical concern. “Tegenaria-domestica-chb” by Chb, CC BY 3.0

Interactive

Where each species has been found in Iowa

Pick a species. The coloured cells are places where somebody photographed one and the identification was confirmed, redrawn as records are added. It thins over roadless country and thickens around towns, because that is where people look.

Coloured cells are verified Loxosceles reclusa records on iNaturalist, brighter where more have been logged. This is where people have found and photographed the species, so it thins out over roadless country and thickens around parks and towns. It is a record map, not a drawn range boundary. See the underlying records.

The season

When spiders come indoors in Iowa

Indoor sightings in Iowa pick up around August 15, peak between September 1 and October 15, and fade by November 10. The wanderers are mature male house spiders and funnel weavers searching for females, plus spring hatched spiders that have finally grown large enough to see. The recluse spiders follow the same calendar because females are at full size; the busiest month in the Iowa record is August.

Recluse spider records in Iowa, by month

13 research grade records of recluse spiders in Iowa, grouped by the month observed.From the iNaturalist snapshot taken 2026-09-19.

What the chart counts. Records, and a record needs a spider and a person with a camera. Spring spikes in some states are a late April bioblitz. Switch to the effort adjusted view and each month is divided by every research grade observation logged in Iowa that month, which strips most of that out. Neither view is a population count.

A large dark funnel weaver spider standing in the white basin of a bathtub, long legs spread on the enamel — A funnel weaver in a bathtub, the classic September find. Smooth enamel is the one surface a wandering male cannot climb back out of, which is why the tub and the sink collect them. “Spinne-Tegenaria-domestica 01” by Traumrune, CC BY-SA 3.0

Identification

The spiders people photograph as recluses

Most spiders reported as a widow or a recluse in Iowa are one of the species below. The tells are visible from a comfortable distance, and a spider left alone in its corner stays there.

A widow is glossy, round bodied, and hangs upside down in a low tangle web with a red or orange hourglass underneath. A recluse is plain tan with six eyes in three pairs, a darker violin on the front segment, and legs with no bands and no spines. A violin shaped mark on its own is not a recluse: many harmless brown spiders carry one, and it is faint on many real recluses. A bite is never an identification. Skin reactions have dozens of causes, and Poison Control on 1-800-222-1222 will ask about symptoms, never for a species name.

Mistaken for a brown recluse

Grass spider or funnel weaver

Agelenopsis

Brown with two dark stripes down the front body segment, long spinnerets at the back, and a flat sheet web with a funnel retreat. A recluse has one violin mark, no stripes, no sheet web, and spins almost nothing.

Woodlouse spider

Dysdera crocata

Red orange front half, cream abdomen, and huge forward pointing jaws. Six eyes like a recluse, which causes the confusion, but the two tone colour is unmistakable and it lives under stones and logs.

Cellar spider

Pholcidae

Thread thin legs many times the body length, hanging in a loose web in basement corners and shaking when disturbed. Tan like a recluse, and nothing else about it is.

Southern house spider

Kukulcania hibernalis

The male is a long legged brown spider that wanders across floors and walls in the South and gets called a recluse constantly. Eight eyes in a tight cluster, a much larger body, and it lives in cracks in outside walls.

If someone is bitten

What to do about a spider bite in Iowa

First

Wash the bite with soap and water. That is the whole of the first aid. Skip creams, heat, ice and anything from a kitchen cupboard.

Then

Call Poison Control on 1-800-222-1222. Free, staffed around the clock, and they will tell you what to watch for over the next hours. They ask about symptoms, never for a species name.

Go to a hospital

For muscle cramping, sweating, spreading pain, or a wound that keeps getting worse over a day or two. Those are the signs that matter after a widow or recluse bite, and treatment depends on them, never on identifying the spider.

About the spider

A bite is never an identification. Skin reactions have dozens of causes and most marks blamed on spiders are something else. If the spider is already dead and in a container, bring it; never hunt for one.

Poison Control: 1-800-222-1222, any time, any state.

Common questions

Iowa spider season FAQ

Why are there so many spiders in my house in Iowa right now?

Are there joro spiders in Iowa?

Are there black widows in Iowa?

Are there brown recluse spiders in Iowa?

Where do widows and recluses live in Iowa?

How do I tell a widow or recluse from a harmless spider?

A widow is glossy, round bodied, and hangs upside down in a low tangle web with a red or orange hourglass underneath. A recluse is plain tan with six eyes in three pairs, a darker violin on the front segment, and legs with no bands and no spines. A violin shaped mark on its own is not a recluse: many harmless brown spiders carry one, and it is faint on many real recluses. A bite is never an identification. Skin reactions have dozens of causes, and Poison Control on 1-800-222-1222 will ask about symptoms, never for a species name.

What should I do if I am bitten by a spider?

Wash the bite with soap and water and call Poison Control on 1-800-222-1222, which is free and staffed around the clock. Go to a hospital for muscle cramping, sweating, spreading pain, or a wound that keeps getting worse over a day or two, which are the signs that matter after a widow or recluse bite. Treatment depends on the symptoms and never on naming the spider, and most marks blamed on spiders have another cause.

Also indoors this season

The rest of your Iowa autumn

Iowa venomous snakesThe other animal people fear on sight, with the same answer: a short real list and a long list of lookalikes.Iowa fall invadersStink bugs, boxelder bugs and lady beetles head for the siding in the same weeks the spiders wander.Iowa rodent seasonMice move toward buildings as the nights cool, and the gaps they use are the gaps spiders use.

More Midwest spider season pages

Species lists, record counts and monthly curves are research grade observations from the iNaturalist API, aggregate counts only, snapshot 2026-09-19 with the curves read live in your browser. They measure how often people find and photograph a species, never how many there are, and a species with no record here may still live here. Season windows are drawn from those curves and are climatological typicals. See every record behind this page. For any bite, wash with soap and water and call Poison Control on 1-800-222-1222. National picture: spider season by state.
Hero image: “Brown-recluse-2”, Br-recluse-guy, Public domain

Spider Season in Iowa: What Lives Here and When It Comes Indoors

Spiders in Iowa, by the numbers