Snakes and spiders in Contra Costa County, California
Contra Costa County, home of Martinez, has 13 snake and 60 spider species on record, from 1,160 licensed snake and 1,469 spider records. Venomous species here: the western rattlesnake and the western black widow.
Are there venomous snakes or spiders in Contra Costa County?
Yes. The western rattlesnake: 192 licensed records, 4% of all California records of it. The western black widow: 71 licensed records, 6% of all California records of it.
What snakes are in Contra Costa County?
In all, 13 snake species are on the Contra Costa County list. The most recorded are the gopher snake (289), the western rattlesnake (192) and the western terrestrial garter snake (125).
| # | Species | Records | Share of California records |
|---|---|---|---|
| 1 | Gopher snake Pituophis catenifer | 289 | 4% |
| 2 | Western rattlesnake venomous Crotalus oreganus | 192 | 4% |
| 3 | Western terrestrial garter snake Thamnophis elegans | 125 | 1% |
| 4 | Ring-necked snake Diadophis punctatus | 113 | 6% |
| 5 | California kingsnake Lampropeltis californiae | 102 | 4% |
| 6 | Sharp-tailed snake Contia tenuis | 99 | 11% |
| 7 | Aquatic garter snake Thamnophis atratus | 60 | 2% |
| 8 | Striped racer Masticophis lateralis | 55 | 4% |
| 9 | Eastern racer Coluber constrictor | 53 | 4% |
| 10 | Northern rubber boa Charina bottae | 17 | 3% |
| 11 | Western aquatic garter snake Thamnophis couchii | 16 | 0% |
| 12 | Coast nightsnake Hypsiglena ochrorhynchus | 11 | 5% |
| 13 | Common garter snake Thamnophis sirtalis | 9 | 0% |
When are snakes out in Contra Costa County?
Observation records of snakes in Contra Costa County run mostly March through October, peaking in May with 24% of them, the same peak as California as a whole.
What spiders are in Contra Costa County?
In all, 60 spider species are on the Contra Costa County list. The most recorded are the Koch's wolf spider (178), the Bay Area blonde (136) and the California turret spider (97). Contra Costa County holds more than half of all California records of Marinarozelotes barbatus, Zelotes puritanus, Drassyllus saphes and Promyrmekiaphila clathrata.
| # | Species | Records | Share of California records |
|---|---|---|---|
| 1 | Koch's wolf spider Alopecosa kochi | 178 | 17% |
| 2 | Bay Area blonde Aphonopelma iodius | 136 | 42% |
| 3 | California turret spider Atypoides riversi | 97 | 25% |
| 4 | Steatoda nobilis | 71 | 4% |
| 5 | Western black widow venomous Latrodectus hesperus | 71 | 6% |
| 6 | California funnel-web spider Calisoga longitarsis | 60 | 36% |
| 7 | Johnson jumper Phidippus johnsoni | 54 | 6% |
| 8 | Bold jumper Phidippus audax | 35 | 1% |
| 9 | Drassyllus insularis | 35 | 18% |
| 10 | Garden spider Araneus diadematus | 33 | 7% |
| 11 | Araneus andrewsi | 28 | 41% |
| 12 | Western lynx spider Oxyopes scalaris | 24 | 2% |
| 13 | Sixspotted orbweaver Araniella displicata | 22 | 10% |
| 14 | Marinarozelotes barbatus | 20 | 67% |
| 15 | Cone-shaped orbweaver Cyclosa conica | 19 | 19% |
| 16 | Colonus hesperus | 18 | 2% |
| 17 | Zelotes puritanus | 18 | 82% |
| 18 | Banded garden spider Argiope trifasciata | 17 | 6% |
| 19 | Micaria utahna | 17 | 45% |
| 20 | Zelotes discens | 15 | 45% |
| 21 | Sierra dome spider Neriene litigiosa | 14 | 16% |
| 22 | False black widow Steatoda grossa | 13 | 1% |
| 23 | Mouse spider Scotophaeus blackwalli | 13 | 5% |
| 24 | Zelotes anthereus | 11 | 35% |
| 25 | Drassyllus saphes | 10 | 71% |
| 26 | Buttonhook leafbeetle jumping spider Sassacus vitis | 9 | 1% |
| 27 | Diaea livens | 9 | 21% |
| 28 | Dysdera crocata | 9 | 1% |
| 29 | Goldenrod crab spider Misumena vatia | 9 | 4% |
| 30 | Gray house spider Badumna longinqua | 9 | 3% |
| 31 | Striped lynx spider Oxyopes salticus | 9 | 1% |
| 32 | Marbled cellar spider Holocnemus pluchei | 8 | 1% |
| 33 | Promyrmekiaphila clathrata | 8 | 73% |
| 34 | Western parson spider Herpyllus propinquus | 8 | 4% |
| 35 | Zoropsid spider Zoropsis spinimana | 8 | 7% |
| 36 | Half-edged wall jumping spider Menemerus semilimbatus | 7 | 0% |
| 37 | Longbodied cellar spider Pholcus phalangioides | 7 | 1% |
| 38 | Oregon paradise jumping spider Habronattus oregonensis | 7 | 5% |
| 39 | Zebra spider Salticus scenicus | 7 | 2% |
| 40 | Zygiella x-notata | 7 | 9% |
| 41 | Black-and-yellow argiope Argiope aurantia | 5 | 3% |
| 42 | Cat-faced spider Araneus gemmoides | 5 | 7% |
| 43 | Green lynx spider Peucetia viridans | 5 | 1% |
| 44 | Habronattus pyrrithrix | 5 | 1% |
| 45 | McCook's split wolf spider Schizocosa mccooki | 5 | 2% |
| 46 | Mecaphesa schlingeri | 5 | 10% |
| 47 | Cyclosa turbinata | 4 | 3% |
| 48 | Hairy tufted jumping spider Phidippus comatus | 4 | 3% |
| 49 | Metaphidippus manni | 4 | 5% |
| 50 | Northern orb weaver Aculepeira packardi | 4 | 11% |
| 51 | California flattened jumping spider Platycryptus californicus | 3 | 3% |
| 52 | Castianeira thalia | 3 | 8% |
| 53 | Habronattus tarsalis | 3 | 1% |
| 54 | Triangulate bud spider Steatoda triangulosa | 3 | 4% |
| 55 | Schizocosa maxima | 2 | 8% |
| 56 | Western spotted orbweaver Neoscona oaxacensis | 2 | 0% |
| 57 | Heliophanus apiatus | 1 | 2% |
| 58 | Bull-headed sac spider Trachelas pacificus | — | — |
| 59 | Phanias harfordi | — | — |
| 60 | Spotted orbweaver Neoscona crucifera | — | — |
When are spiders out in Contra Costa County?
Observation records of spiders in Contra Costa County run through most of the year, peaking in September with 16% of them; across California the peak is April.
What stands out in Contra Costa County
Species for which Contra Costa County holds a large share of all California records: Zelotes puritanus, 82% (18 of 22); Marinarozelotes barbatus, 67% (20 of 30); Zelotes discens, 45% (15 of 33); Micaria utahna, 45% (17 of 38); the Bay Area blonde, 42% (136 of 320); Araneus andrewsi, 41% (28 of 68); the California funnel-web spider, 36% (60 of 165); Zelotes anthereus, 35% (11 of 31).
Common in California, not on the Contra Costa County list
Among the snakes most recorded across California, these do not reach the county list: 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 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 Contra Costa 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 and the triangulate bud spider. 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.
Contra Costa County among California counties
By licensed snake records Contra Costa County ranks 20th 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 San Mateo 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.