Venomous snakes and spiders in Illinois

Illinois's venomous snakes are two copperhead or cottonmouth species and two rattlesnake species. Together they account for 349 licensed records; the northern cottonmouth alone has 74% of them, and the least recorded, the timber rattlesnake, has 20.

Two widow species (Southern black widow: 19 records, Northern black widow: 18 records) and one recluse species (Brown recluse: 313 records) are on the Illinois list. Widow bites cause muscle pain and cramps; recluse bites can cause a slow-healing wound. Both are rare and seldom fatal.

Yes. One scorpion species is recorded in Illinois, from 45 licensed records: Striped bark scorpion (35 records). Every scorpion has venom; only the Arizona bark scorpion's sting is medically significant, and it is not on the Illinois list.

These eight account for 58% of all licensed snake records in Illinois; the most recorded, the common garter snake, alone for 15%.

These eight account for 11% of all licensed spider records in Illinois; the most recorded, Pardosa saxatilis, alone for 3%.

Observation records of venomous snakes in Illinois run mostly April through October, peaking in October with 58% of them. December through February together hold under 2% of the records, so venomous snakes in Illinois are rarely recorded in winter.

Observation records of spiders in Illinois run mostly April through October, peaking in September with 20% of them. December through February together hold under 2% of the records, so spiders in Illinois are rarely recorded in winter.

Union County has the most records of venomous snakes in Illinois, 229, most of them of the northern cottonmouth. Jackson County and Johnson County follow.

Union County leads with 424 records (15%), followed by Cook County and Lake County; the top five counties hold 44% of the total. 90 of Illinois's 102 counties have at least one licensed snake record.

Illinois counties with their own page: Champaign County, Cook County, Effingham County, Iroquois County, Jo Daviess County, Lee County, Marion County, Mason County, Union County and Will County.

Yes. Illinois has four venomous snake species on its list, the kind people usually call poisonous: northern cottonmouth, eastern copperhead, eastern massasauga and timber rattlesnake. Strictly, snakes are venomous (they inject venom), not poisonous (harmful to eat or touch).

Yes. Two species are on the Illinois list: the eastern massasauga and the timber rattlesnake, with 41 licensed records between them.

Yes. One species is on the Illinois list: the eastern copperhead, with 49 licensed records. Most licensed records of the eastern copperhead come from Union County, Jersey County and Jackson County.

Yes. One species is on the Illinois list: the northern cottonmouth, with 259 licensed records. Most licensed records of the northern cottonmouth come from Union County, Johnson County and Jackson County.

No. GBIF holds no coral snake record for Illinois under any license.

Illinois has 259 licensed records of the northern cottonmouth, which ranks the state 7th of the 16 states where it reaches our threshold. Its observation records in Illinois run mostly March through October, peaking in October; most licensed records come from Union County, Johnson County and Jackson County. Range in other states and photos: Northern cottonmouth profile.

Illinois has 49 licensed records of the eastern copperhead, which ranks the state 21st of the 27 states where it reaches our threshold. Most of its licensed records in Illinois come from Union County, Jersey County and Jackson County. Range in other states and photos: Eastern copperhead profile.

Illinois has 21 licensed records of the eastern massasauga, which ranks the state 5th of the 8 states where it reaches our threshold. Range in other states and photos: Eastern massasauga profile.

Illinois has 20 licensed records of the timber rattlesnake, which ranks the state 24th of the 30 states where it reaches our threshold. Range in other states and photos: Timber rattlesnake profile.

Many snakes and spiders taken for venomous ones are harmless species with a similar look. These are the usual confusions, with each species' licensed records in Illinois.

Copperheads: 49 licensed records in Illinois. Harmless species often taken for them are also on the state list: northern water snake (243), eastern rat snake (86), plain-bellied watersnake (72), eastern hog-nosed snake (60) and eastern milksnake (59). Together they have 520 licensed records, and the lookalikes are recorded 11 times as often.

Cottonmouths: 259 licensed records in Illinois. Harmless species often taken for them are also on the state list: northern water snake (243), plain-bellied watersnake (72), diamondback water snake (26), mud snake (8) and green water snake (4). Together they have 353 licensed records, and the two sides are recorded about equally.

Rattlesnakes: 41 licensed records in Illinois. Harmless species often taken for them are also on the state list: eastern fox snake (83), eastern hog-nosed snake (60), gopher snake (26) and plains hog-nosed snake (1). Together they have 170 licensed records, and the lookalikes are recorded 4 times as often.

No coral snakes reach the Illinois list, and GBIF holds no coral snake record for Illinois under any license, so a snake taken for one here is most likely a harmless lookalike. Those recorded in the state: eastern milksnake (59).

Widow spiders: 37 licensed records in Illinois. Harmless species often taken for them are also on the state list: triangulate bud spider (72), common house spider (26), boreal combfoot (25) and twospotted cobweb spider (14). Together they have 137 licensed records, and the lookalikes are recorded 4 times as often.

Recluse spiders: 313 licensed records in Illinois. Harmless species often taken for them are also on the state list: Pennsylvania grass spider (63), longbodied cellar spider (29) and spitting spider (3). Together they have 95 licensed records, and here the venomous species are the more recorded side, 3.3 to 1.

By count of venomous snake species, Illinois ranks 18th of 50 states, level with Nebraska. Nationally, Arizona leads with 14 species; five list none.

Of the five states bordering Illinois, Missouri lists more venomous snake species (Illinois: 4 species; Missouri 5, Indiana 3, Iowa 3, Kentucky 3, Wisconsin 2).

Venomous snakes listed next door but not in Illinois: the prairie rattlesnake (Iowa); the pygmy rattlesnake (Missouri); the western massasauga (Missouri). The most widely shared is the timber rattlesnake, listed in all five bordering states.

Yes. Two widow species are on the Illinois list: the southern black widow (19 records) and the northern black widow (18 records).

Yes. The brown recluse is on the Illinois list, with 313 licensed records. Most of its licensed records come from Warren County, DeKalb County and Champaign County.

Illinois has 313 licensed records of the brown recluse, which ranks the state 1st of the 16 states where it reaches our threshold. Most of its licensed records in Illinois come from Warren County, DeKalb County and Champaign County. Range in other states and photos: Brown recluse profile.

Illinois has 19 licensed records of the southern black widow, which ranks the state 14th of the 22 states where it reaches our threshold. Range in other states and photos: Southern black widow profile.

Illinois has 18 licensed records of the northern black widow, which ranks the state 10th of the 30 states where it reaches our threshold. Range in other states and photos: Northern black widow profile.