Snakes and spiders in San Mateo County, California
San Mateo County has 12 snake and 48 spider species on record, from 2,376 licensed snake and 743 spider records. Venomous species here: the western rattlesnake and the western black widow.
Are there venomous snakes or spiders in San Mateo County?
Yes. The western rattlesnake: 82 licensed records, 2% of all California records of it. The western black widow: 12 licensed records, 1% of all California records of it.
What snakes are in San Mateo County?
In all, 12 snake species are on the San Mateo County list. The most recorded are the western terrestrial garter snake (770), the common garter snake (446) and the gopher snake (284).
| # | Species | Records | Share of California records |
|---|---|---|---|
| 1 | Western terrestrial garter snake Thamnophis elegans | 770 | 4% |
| 2 | Common garter snake Thamnophis sirtalis | 446 | 8% |
| 3 | Gopher snake Pituophis catenifer | 284 | 4% |
| 4 | Aquatic garter snake Thamnophis atratus | 265 | 7% |
| 5 | Eastern racer Coluber constrictor | 199 | 16% |
| 6 | Ring-necked snake Diadophis punctatus | 165 | 9% |
| 7 | Western rattlesnake venomous Crotalus oreganus | 82 | 2% |
| 8 | Northern rubber boa Charina bottae | 47 | 7% |
| 9 | Forest sharp-tailed snake Contia longicauda | 42 | 38% |
| 10 | Sharp-tailed snake Contia tenuis | 31 | 3% |
| 11 | California kingsnake Lampropeltis californiae | 27 | 1% |
| 12 | Striped racer Masticophis lateralis | 7 | 1% |
When are snakes out in San Mateo County?
Observation records of snakes in San Mateo County run mostly March through October, peaking in April with 22% of them; across California the peak is May.
What spiders are in San Mateo County?
In all, 48 spider species are on the San Mateo County list. The most recorded are the California turret spider (94), Steatoda nobilis (46) and the goldenrod crab spider (38).
| # | Species | Records | Share of California records |
|---|---|---|---|
| 1 | California turret spider Atypoides riversi | 94 | 24% |
| 2 | Steatoda nobilis | 46 | 2% |
| 3 | Goldenrod crab spider Misumena vatia | 38 | 17% |
| 4 | Gray house spider Badumna longinqua | 33 | 10% |
| 5 | Beach-dwelling jumping spider Terralonus californicus | 31 | 34% |
| 6 | Johnson jumper Phidippus johnsoni | 29 | 3% |
| 7 | Sixspotted orbweaver Araniella displicata | 26 | 12% |
| 8 | Koch's wolf spider Alopecosa kochi | 18 | 2% |
| 9 | Longbodied cellar spider Pholcus phalangioides | 17 | 2% |
| 10 | Garden spider Araneus diadematus | 16 | 4% |
| 11 | Sierra dome spider Neriene litigiosa | 16 | 19% |
| 12 | Buttonhook leafbeetle jumping spider Sassacus vitis | 14 | 2% |
| 13 | False black widow Steatoda grossa | 13 | 1% |
| 14 | Western black widow venomous Latrodectus hesperus | 12 | 1% |
| 15 | Dysdera crocata | 11 | 2% |
| 16 | Shamrock orbweaver Araneus trifolium | 11 | 20% |
| 17 | Banded garden spider Argiope trifasciata | 9 | 3% |
| 18 | California funnel-web spider Calisoga longitarsis | 8 | 5% |
| 19 | Mouse spider Scotophaeus blackwalli | 8 | 3% |
| 20 | Proszynski's jumping spider Evarcha proszynskii | 8 | 19% |
| 21 | Zebra spider Salticus scenicus | 8 | 3% |
| 22 | Colonus hesperus | 7 | 1% |
| 23 | Diaea livens | 7 | 16% |
| 24 | Pelegrina aeneola | 7 | 7% |
| 25 | Versicolor long-jawed orbweaver Tetragnatha versicolor | 7 | 18% |
| 26 | Bold jumper Phidippus audax | 6 | 0% |
| 27 | Cone-shaped orbweaver Cyclosa conica | 6 | 6% |
| 28 | Heliophanus apiatus | 6 | 11% |
| 29 | Western lynx spider Oxyopes scalaris | 6 | 1% |
| 30 | Zoropsid spider Zoropsis spinimana | 6 | 5% |
| 31 | Metaphidippus manni | 5 | 6% |
| 32 | Habronattus pyrrithrix | 4 | 0% |
| 33 | Arabesque orbweaver Neoscona arabesca | 3 | 7% |
| 34 | Bay Area blonde Aphonopelma iodius | 3 | 1% |
| 35 | Cyclosa turbinata | 3 | 2% |
| 36 | Mexigonus morosus | 3 | 11% |
| 37 | Phanias harfordi | 3 | 8% |
| 38 | Striped lynx spider Oxyopes salticus | 3 | 0% |
| 39 | Flatmesh weaver Oecobius navus | 2 | 1% |
| 40 | Oregon paradise jumping spider Habronattus oregonensis | 2 | 1% |
| 41 | Spotted orbweaver Neoscona crucifera | 2 | 1% |
| 42 | Black-and-yellow argiope Argiope aurantia | 1 | 1% |
| 43 | Bowl and doily spider Frontinella pyramitela | 1 | 1% |
| 44 | Castianeira thalia | 1 | 3% |
| 45 | Common candy-striped spider Enoplognatha ovata | 1 | 9% |
| 46 | Green lynx Peucetia longipalpis | 1 | 3% |
| 47 | Marbled cellar spider Holocnemus pluchei | 1 | 0% |
| 48 | Phanias albeolus | — | — |
When are spiders out in San Mateo County?
Observation records of spiders in San Mateo County run through most of the year, peaking in April with 15% of them, the same peak as California as a whole.
What stands out in San Mateo County
Species for which San Mateo County holds a large share of all California records: the forest sharp-tailed snake, 38% (42 of 110); the beach-dwelling jumping spider, 34% (31 of 92); the California turret spider, 24% (94 of 389); the shamrock orbweaver, 20% (11 of 56); the sierra dome spider, 19% (16 of 85); the goldenrod crab spider, 17% (38 of 228); the eastern racer, 16% (199 of 1,270).
Common in California, not on the San Mateo County list
Among the snakes most recorded across California, these do not reach the county list: the western aquatic garter snake (3,716 statewide), the sidewinder (1,923 statewide), the two-striped garter snake (1,620 statewide), the western shovel-nosed snake (1,482 statewide) and the glossy snake (1,425 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 California, these do not reach the county list: the half-edged wall jumping spider (2,178 statewide) and the brown widow (776 statewide). Few records here can mean the species is rare in the county, or that few people have looked.
Harmless lookalikes in San Mateo County
Rattlesnakes are on the county list, and so are harmless species often taken for them: the gopher snake. Widow spiders are on the county list, and so are harmless species often taken for them: the false black widow. No recluse spiders reach the county list, but the desert recluse is on the California list: treat any spider like it as venomous until identified. Harmless species often taken for them here: the longbodied cellar spider.
San Mateo County among California counties
By licensed snake records San Mateo County ranks 8th of 58 California counties with any.
Other California counties with their own page: San Diego County, Lassen County, Shasta County, Riverside County, San Bernardino County, Humboldt County, Sonoma County and Los Angeles County.
The whole state: venomous species in California, all snakes, all spiders.
GBIF records read 2026-09-29. Listed: any license. Counted: CC0/CC BY only. How we count.