Spider Season in Illinois: What Lives Here and When It Comes Indoors
2 widow or recluse species have verified records in Illinois. The indoor season, a live range map, and the lookalikes.
Spiders are moving indoors in Illinois nowSpiders in Illinois, by the numbers
Verified records, snapshot 2026-09-19 first records 2025Illinois runs from brown recluse country in the south, 267 verified records around the Metro East and the Shawnee Hills, to yellow sac spider country in Chicago. The northern black widow, 146 records, is the state's widow, and one joro record in 2025 is the first.
The first joro records in Illinois
Illinois has 1 verified joro spider record, the earliest from 2025. A first record is a photographed spider, never a population. Whether the species takes hold here will show in the year by year series on the national page over the next few autumns.
Where the years come from. The joro spider was first confirmed in North America in 2014, from specimens collected in Barrow, Jackson and Madison counties, northeast Georgia (Hoebeke, Huffmaster and Freeman (2015), PeerJ 3:e763). Every other year on this page is a first iNaturalist record, which runs later than the collections a species is established on.
The 2 widow and recluse species recorded in Illinois
Every species below has verified, photograph backed records in Illinois. 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 | 267 | 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. |
| Northern black widow Latrodectus variolus | Widow | 146 | The hourglass is usually split into two red bars, often with a row of red spots along the top of the abdomen. Woodland edges, stumps, stone walls and old outbuildings; the widow of the Northeast and the Great Lakes. |
- Northern yellow sac spider (Cheiracanthium mildei, 106 records): A small pale yellow green spider that walks ceilings and window frames at night and rests in a silk sac in a corner by day. The spider most often met indoors across the Northeast and upper Midwest.
Where each species has been found in Illinois
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 Trichonephila clavata 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.
When spiders come indoors in Illinois
Indoor sightings in Illinois 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 widow spiders follow the same calendar because females are at full size; the busiest month in the Illinois record is June.
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 Illinois that month, which strips most of that out. Neither view is a population count.
The spiders people photograph as recluses and widows
Most spiders reported as a widow or a recluse in Illinois 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.
Mistaken for a black widow
False widow
Steatoda grossa
Purplish brown rather than glossy black, with pale markings on top of the abdomen and nothing underneath. The same tangle web in the same corners, which is why it is photographed as a widow more than any other spider.
Triangulate cobweb spider
Steatoda triangulosa
Small, brown, with a row of pale triangles down the abdomen. Lives in the same low corners and window frames a widow would, and turns up indoors far more often.
Common house spider
Parasteatoda tepidariorum
Mottled tan and brown with a rounded abdomen, in messy cobwebs in ceiling corners, under eaves and behind furniture. The most photographed spider in American houses, and an autumn indoor regular.
Mistaken for a joro spider
Yellow garden spider
Argiope aurantia
Black and yellow, but the abdomen is egg shaped with a bold black and yellow pattern rather than banded, the legs are black with a yellow base instead of banded along their length, and the web has a thick zigzag of white silk down the middle. Native, and in every state.
Banded garden spider
Argiope trifasciata
Silvery white with thin black and yellow bands across the abdomen, on a wheel shaped web in tall grass and gardens in late summer. Smaller than a joro, with shorter legs and no red underneath.
Golden silk orbweaver
Trichonephila clavipes
The joro's native cousin across the Deep South. Orange brown rather than yellow and black, with tufts of dark hair on the leg joints and no red patch. It has been in the Southeast for as long as there are records.
What to do about a spider bite in Illinois
Poison Control: 1-800-222-1222, any time, any state.
Illinois spider season FAQ
The rest of your Illinois autumn
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: “Adult Female Black Widow” by Shenrich91, CC BY-SA 3.0