Snakes and spiders in Union County, Illinois
Union County, home of Jonesboro, has 20 snake and 15 spider species on record, from 424 licensed snake and 310 spider records. Venomous species here: the northern cottonmouth, the eastern copperhead, the timber rattlesnake and the northern black widow.
Are there venomous snakes or spiders in Union County?
Yes. The northern cottonmouth: 212 licensed records, 82% of all Illinois records of it. The eastern copperhead: 17 licensed records, 35% of all Illinois records of it. The timber rattlesnake: 6 licensed records, 30% of all Illinois records of it. The northern black widow: 4 licensed records, 22% of all Illinois records of it.
What snakes are in Union County?
In all, 20 snake species are on the Union County list. The most recorded are the northern cottonmouth (212), the plain-bellied watersnake (35) and the rough greensnake (31). Union County holds more than half of all Illinois records of the northern cottonmouth, the rough greensnake, the green water snake and the mud snake.
| # | Species | Records | Share of Illinois records |
|---|---|---|---|
| 1 | Northern cottonmouth venomous Agkistrodon piscivorus | 212 | 82% |
| 2 | Plain-bellied watersnake Nerodia erythrogaster | 35 | 49% |
| 3 | Rough greensnake Opheodrys aestivus | 31 | 53% |
| 4 | Ring-necked snake Diadophis punctatus | 24 | 28% |
| 5 | Eastern rat snake Pantherophis alleghaniensis | 22 | 26% |
| 6 | Eastern copperhead venomous Agkistrodon contortrix | 17 | 35% |
| 7 | Western ribbon snake Thamnophis proximus | 16 | 32% |
| 8 | Eastern racer Coluber constrictor | 11 | 9% |
| 9 | DeKay's brown snake Storeria dekayi | 9 | 3% |
| 10 | Timber rattlesnake venomous Crotalus horridus | 6 | 30% |
| 11 | Common garter snake Thamnophis sirtalis | 4 | 1% |
| 12 | Diamondback water snake Nerodia rhombifer | 4 | 15% |
| 13 | Eastern black kingsnake Lampropeltis nigra | 4 | 17% |
| 14 | Eastern wormsnake Carphophis amoenus | 4 | 5% |
| 15 | Green water snake Nerodia cyclopion | 4 | 100% |
| 16 | Mud snake Farancia abacura | 4 | 50% |
| 17 | Northern water snake Nerodia sipedon | 4 | 2% |
| 18 | Red-bellied snake Storeria occipitomaculata | 4 | 10% |
| 19 | Eastern milksnake Lampropeltis triangulum | 3 | 5% |
| 20 | Smooth earth snake Virginia valeriae | 2 | 11% |
When are snakes out in Union County?
Observation records of snakes in Union County run mostly March through October, peaking in October with 56% of them, the same peak as Illinois as a whole.
What spiders are in Union County?
In all, 15 spider species are on the Union County list. The most recorded are Pirata sedentarius (15), the brush-legged split wolf spider (11) and Phrurotimpus alarius (11). Union County holds more than half of all Illinois records of Pirata sedentarius.
| # | Species | Records | Share of Illinois records |
|---|---|---|---|
| 1 | Pirata sedentarius | 15 | 54% |
| 2 | Brush-legged split wolf spider Schizocosa ocreata | 11 | 6% |
| 3 | Phrurotimpus alarius | 11 | 8% |
| 4 | Orchard orbweaver Leucauge venusta | 9 | 8% |
| 5 | Dark fishing spider Dolomedes tenebrosus | 8 | 9% |
| 6 | Nursery web spider Pisaurina mira | 7 | 6% |
| 7 | Marbled orbweaver Araneus marmoreus | 6 | 16% |
| 8 | Spotted orbweaver Neoscona crucifera | 5 | 3% |
| 9 | Arrowhead orbweaver Verrucosa arenata | 4 | 11% |
| 10 | Northern black widow venomous Latrodectus variolus | 4 | 22% |
| 11 | Spined micrathena Micrathena gracilis | 4 | 4% |
| 12 | Black-and-yellow argiope Argiope aurantia | 2 | 2% |
| 13 | Sixspotted fishing spider Dolomedes triton | 2 | 4% |
| 14 | Bold jumper Phidippus audax | 1 | 0% |
| 15 | Georgia wolf spider Tigrosa georgicola | 1 | 10% |
When are spiders out in Union County?
Observation records of spiders in Union County run mostly April through October, peaking in October with 44% of them; across Illinois the peak is September.
What stands out in Union County
Species for which Union County holds a large share of all Illinois records: the northern cottonmouth, 82% (212 of 259); Pirata sedentarius, 54% (15 of 28); the rough greensnake, 53% (31 of 58); the plain-bellied watersnake, 49% (35 of 72); the eastern copperhead, 35% (17 of 49); the western ribbon snake, 32% (16 of 50); the ring-necked snake, 28% (24 of 87); the eastern rat snake, 26% (22 of 86).
Common in Illinois, not on the Union County list
Among the snakes most recorded across Illinois, these do not reach the county list: the plains garter snake (250 statewide), the eastern fox snake (83 statewide) and the prairie kingsnake (82 statewide). Few records here can mean the species is rare in the county, or that few people have looked.
Among the spiders most recorded across Illinois, these do not reach the county list: Pardosa saxatilis (545 statewide), the brown recluse (313 statewide), Piratula minuta (208 statewide), the pale sheetweb weaver (196 statewide), the tan crab spider (187 statewide) and the zebra spider (173 statewide). Few records here can mean the species is rare in the county, or that few people have looked.
Harmless lookalikes in Union County
Copperheads are on the county list, and so are harmless species often taken for them: the plain-bellied watersnake, the eastern rat snake, the northern water snake and the eastern milksnake. Cottonmouths are on the county list, and so are harmless species often taken for them: the plain-bellied watersnake, the diamondback water snake, the green water snake and the mud snake. No coral snakes reach the county list, and GBIF holds no coral snake record for Illinois under any license, so one reported here is most likely a harmless lookalike: the eastern milksnake.
Union County among Illinois counties
By licensed snake records Union County ranks 1st of 90 Illinois counties with any.
Other Illinois counties with their own page: Cook County, Will County, Champaign County, Jo Daviess County, Mason County, Iroquois County, Effingham County and Lee County.
The whole state: venomous species in Illinois, all snakes, all spiders.
GBIF records read 2026-09-29. Listed: any license. Counted: CC0/CC BY only. How we count.