Snakes and spiders in Mason County, Illinois
Mason County, home of Havana, has 4 snake and 5 spider species on record, from 32 licensed snake and 543 spider records. No venomous snake or spider reaches the county list, but the northern cottonmouth, the eastern copperhead, the eastern massasauga, the timber rattlesnake and 3 more are on the Illinois list: treat any snake or spider like them as venomous until identified.
What snakes are in Mason County?
In all, 4 snake species are on the Mason County list. The most recorded are the common garter snake (4), the eastern racer (4) and the eastern hog-nosed snake (3).
| # | Species | Records | Share of Illinois records |
|---|---|---|---|
| 1 | Common garter snake Thamnophis sirtalis | 4 | 1% |
| 2 | Eastern racer Coluber constrictor | 4 | 3% |
| 3 | Eastern hog-nosed snake Heterodon platirhinos | 3 | 5% |
| 4 | Gopher snake Pituophis catenifer | 2 | 8% |
What spiders are in Mason County?
In all, 5 spider species are on the Mason County list. The most recorded are Habronattus agilis (23), Schizocosa retrorsa (22) and the tan crab spider (19). Mason County holds more than half of all Illinois records of Habronattus agilis and Schizocosa retrorsa.
| # | Species | Records | Share of Illinois records |
|---|---|---|---|
| 1 | Habronattus agilis | 23 | 88% |
| 2 | Schizocosa retrorsa | 22 | 67% |
| 3 | Tan crab spider Xysticus ferox | 19 | 10% |
| 4 | Lined orbweaver Mangora gibberosa | 11 | 33% |
| 5 | Black-and-yellow argiope Argiope aurantia | 3 | 2% |
What stands out in Mason County
Species for which Mason County holds a large share of all Illinois records: Habronattus agilis, 88% (23 of 26); Schizocosa retrorsa, 67% (22 of 33); the lined orbweaver, 33% (11 of 33).
Common in Illinois, not on the Mason County list
Among the spiders most recorded across Illinois, these do not reach the county list: Pardosa saxatilis (545 statewide), the bold jumper (344 statewide), the brown recluse (313 statewide), Piratula minuta (208 statewide), the pale sheetweb weaver (196 statewide) and the brush-legged split wolf spider (192 statewide). Few records here can mean the species is rare in the county, or that few people have looked.
Harmless lookalikes in Mason County
No copperheads reach the county list, but the eastern copperhead is on the Illinois list: treat any snake like it as venomous until identified. Harmless species often taken for them here: the eastern hog-nosed snake. No rattlesnakes reach the county list, but the eastern massasauga and the timber rattlesnake are on the Illinois list: treat any snake like them as venomous until identified. Harmless species often taken for them here: the eastern hog-nosed snake and the gopher snake.
Mason County among Illinois counties
By licensed snake records Mason County ranks 21st of 90 Illinois counties with any.
Other Illinois counties with their own page: Union County, Cook County, Will County, Champaign County, Jo Daviess 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.