Venomous spiders in Illinois

Venomous spiders living in Illinois

2species

Black widow, Brown recluse.

How to recognize them

Black widow Latrodectus mactans, L. variolus, L. hesperus

Shiny black female with a round abdomen
Red hourglass or two red marks under the abdomen
Messy, strong web low to the ground, often in garages, wood piles and water meters

Brown recluse Loxosceles reclusa

Dark violin shape on the back, neck of the violin points to the rear
Six eyes in three pairs (most spiders have eight)
Plain tan abdomen and legs with no bands or spines

Almost all spiders have venom, but very few can hurt people. We list the ones with medically significant bites plus a few that people often worry about.

Counties with records

None recorded
1 species
2
3 to 4
5 or more

Venomous spiders with open GBIF records, by county: 60 counties so far. Blank does not mean absent.

Active months

Open records of venomous spiders in Illinois by month; most fall in June to September.

Harmless spiders people mistake for them

Brown Recluse vs Wolf Spider Wolf spider: harmless
Brown Recluse vs Cellar Spider Cellar spider: harmless

Quick answers

Questions

How many venomous spiders are in Illinois?

2 species live in the state: Black widow and Brown recluse.

Which venomous spiders in Illinois are dangerous?

Black widow and Brown recluse: bites or stings need medical care.

When are venomous spiders most active in Illinois?

Most open records fall in June to September.

Which harmless spiders get mistaken for venomous ones in Illinois?

Wolf spider and Cellar spider. See the side-by-side comparisons below.