A Guide to the Amphibians
and Reptiles of California

Southwestern Threadsnake - Rena humilis humilis

(Baird and Girard, 1853)

(= Southwestern Blind Snake - Leptotyphlops humilis humilis)
Click on a picture for a larger view

Threadsnakes California Range Map
Range in California: Red

Orange: Desert Threadsnake

observation link

Southwestern Threadsnake
Adult, San Diego County
Southwestern Threadsnake Southwestern Threadsnake Southwestern Threadsnake Southwestern Threadsnake
Adult 1, coastal San Diego County
Southwestern Threadsnake Southwestern Threadsnake Southwestern Threadsnake Southwestern Threadsnake
Adult 2, coastal San Diego County
Southwestern Threadsnake Southwestern Threadsnake Southwestern Threadsnake Southwestern Threadsnake
Threadsnakes will sometimes enter homes. Jerry McMurry discovered this snake in his home one summer night in coastal San Diego County.
Adult, San Bernardino County
© Patrick Briggs
Hatchling, Inyo County
© Adam G. Clause
Pink adult, Inyo County
© Adam G. Clause
Southwestern Threadsnake Southwestern Threadsnake Southwestern Threadsnake Southwestern Threadsnake
Juvenile, Orange County © Ivan Vershynin Adult, Mono County
© Adam G. Clause
Subadult, Mono County
© Adam G. Clause
Southwestern Threadsnake Southwestern Threadsnake Southwestern Threadsnake Southwestern Threadsnake
Adult, San Diego County © Paul Maier Adult, Orange County © Ivan Vershynin
Southwestern Threadsnake Habitat Southwestern Threadsnake Habitat Southwestern Threadsnake Habitat snake habitat
Habitat, 1500 ft., San Gabriel Mountains, Los Angeles County San Diego County coastal sage habitat Habitat, San Diego County Habitat, Riverside County 
riparian canyon
Southwestern Threadsnake Habitat Rosy Boa Habitat Rosy Boa Habitat  
Habitat, San Diego County

Habitat, Riverside County
riparian canyon
Habitat, Orange County
© Ivan Vershynin
Short Video
  Southwestern Threadsnake    
  A Southwestern Threadsnake discovered on a cool spring morning races across it's coastal San Diego County habitat with amazing speed.    

Not Dangerous (Non-poisonous)  -  This snake does not have venom that is dangerous to most humans.

Adults 7 - 16 inches long (18-41 cm). Hatchlings are around 4 - 5 inches long (10 - 12.7 cm).

A very thin snake with a blunt head and tail.
The tail is tipped with a small spine.
Eyes are nonfunctional dark spots visible under translucent plates.
The scales are shiny and cycloid.
Belly plates are not enlarged.
The lower jaw is countersunk.
Color and Pattern
Coloring is brown, purple, or pink. This snake can be mistaken for a large worm.

Similar Snakes in California
There are two subspecies of Western Treadsnake in California. There is also a very similar non-native blindsnake that has been introduced into Southern California and is gradually increasing its range in the state - the Brahminy Blindsnake.

Go to this page to see more information about comparing the Western Threadsnake with the Brahminy Blindsnake, and suggestions about what to do if you think you have found a Brahminy Blindsnake in California.

Life History and Behavior

Nocturnal. Occasionally found crawling exposed on surface at night. Sometimes seen crawling on paved roads at night. Hides in cracks and under surface debris in daytime. Sometimes found under rocks, boards, or other surface debris where the soil is slightly moist.
When threatened, this snake often writhes around, forming a tight coil while releasing pungent fluids from the cloaca. These fluids serve to repel defensive attacks by the ants and termites on which it feeds. May also play dead.
Diet and Feeding
Eats ants and termites and their larvae and pupae, and occasionally other small insects.

When hunting for food, burrows under roots, rocks, and into ants nests.
Slender body allows them to forage in their ant and termite prey's burrow systems.
Mates in the spring, lays eggs July - August.
Females tend to the eggs, and may use communal nests.

Inhabits areas where the soil is suitable for burrowing: brushy mountain slopes, deserts, rocky hillsides, washes near streams, beach sand.

Geographical Range
This subspecies, Rena humilis humilis - Southwestern Threadsnake, occurs along the Southern California coast - east, north of the range of R.h.cahuilae, into southern Nevada and western Arizona, - south along the west coast of Baja California, - and north, on the east side of the Sierra Nevada mountains, with isolated records from the Sierra Nevada/Tehachapi Mountains region at 9 mile canyon and Jawbone canyon.

The first Mono County record and the northernmost records for this species were documented from the southeastern Chalfant Valley in 2016.
Herpetological Review 47(2), 2016

Finding information about the ranges of the subspecies of Rena humilis is difficult, because they are not recognized by many herpetologists. Some field guides show no subspecies. Some show the range of R. h. humilis extending as far north of Needles, while others show it ranging to just north of the Riverside County border at the Colorado River, as I have decided to show on my map, although I am not certain that it is accurate.There is almost no information about the other subspecies found in Mexico so I have not tried to show them on my map.

The species Rena humilis - Western Threadsnake, is found from Southern California east through southern Arizona and New Mexico, into southwestern Texas, and south into Mexico and Baja California, Mexico.

Full Species Range Map
(Several subspecies are sometimes recognized, but I don't know their exact ranges outside of California.)
Notes on Taxonomy
Some herpetologists do not recognize subspecies of Rena humilis. Those who do recognize four subspecies in the United States, and five in Mexico.

In 2009, Adalsteinsson, Branch, Trape, Vitt & Hedges (Molecular Phylogeny, Classification, and Biogeograpy of Snakes of the Family Leptotyphlopidae (Reptilia, Squamata). Zootaxa. 2240: pp. 1 - 50) placed this species in the genus Rena, making it Rena cahuilae.

Alternate and Previous Names (Synonyms)

Rena humilis humilis - Southwestern Threadsnake
Leptotyphlps humilis - Western Blind Snake (Stebbins 1966, 1985, 2003, Stebbins & Mcginnis 2012)
Leptotyphlps humilis humilis - Western Worm Snake (Stebbins 1954)
Leptotyphlps humilis humilis - Western worm snake (Van Denburgh 1922)
Worm snake (Stejneger 1891)
Humble sheep snake (Cronise 1868)

Blind snake
Brown blind snake
California blind snake
California rena
California worm snake
Cedros island worm snake
Sheep-nosed snake

Conservation Issues  (Conservation Status)
Family Renadae ? Threadsnakes (Blind Snakes) Fitzinger, 1843
Genus Rena Threadsnakes Fitzinger, 1843
Species humilis Western Threadsnake Baird and Girard, 1853

humilis Southwestern Threadsnake (Baird and Girard, 1853)
Original Description
Leptotyphlops- Fitzinger, 1843 - Syst. Rept., p. 24
Leptotyphlops humilis - (Baird and Girard, 1853) - Cat. N. Amer. Rept., Pt. 1, p. 143

from Original Description Citations for the Reptiles and Amphibians of North America © Ellin Beltz

Meaning of the Scientific Name
Rena = either Latin - Reborn, or Greek - Peace

- Latin - small or ground dwelling -- no specific reason in original description.

from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz

Related or Similar California Snakes
R. h. cahuilae - Desert Threadsnake

More Information and References
California Department of Fish and Wildlife

Stebbins, Robert C., and McGinnis, Samuel M.  Field Guide to Amphibians and Reptiles of California: Revised Edition (California Natural History Guides) University of California Press, 2012.

Stebbins, Robert C. California Amphibians and Reptiles. The University of California Press, 1972.

Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003.

Behler, John L., and F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992.

Powell, Robert., Joseph T. Collins, and Errol D. Hooper Jr. A Key to Amphibians and Reptiles of the Continental United States and Canada. The University Press of Kansas, 1998.

Bartlett, R. D. & Patricia P. Bartlett. Guide and Reference to the Snakes of Western North America (North of Mexico) and Hawaii. University Press of Florida, 2009.

Bartlett, R. D. & Alan Tennant. Snakes of North America - Western Region. Gulf Publishing Co., 2000.

Brown, Philip R. A Field Guide to Snakes of California. Gulf Publishing Co., 1997.

Ernst, Carl H., Evelyn M. Ernst, & Robert M. Corker. Snakes of the United States and Canada. Smithsonian Institution Press, 2003.

Wright, Albert Hazen & Anna Allen Wright. Handbook of Snakes of the United States and Canada. Cornell University Press, 1957.

Conservation Status

The following conservation status listings for this animal are taken from the August 2019 California Natural Diversity Database (CNDDB) Special Animals List and the CNDDB 2019 Endangered and Threatened Animals List, both of which are published by the California Department of Fish and Wildlife.

The status listings here might not be the most current. Check the CDFW CNDDB website to see if there are more current lists:

If no status is listed here, the animal is not included on either CDFW CNDDB list. This most likely indicates that there are no serious conservation concerns for the animal. To find out more about an animal's status, you can go to the NatureServe and IUCN websites to check their rankings.

This snake is not included on the Special Animals List, which indicates that there are no significant conservation concerns for it in California.
Organization Status Listing  Notes
NatureServe Global Ranking
NatureServe State Ranking
U.S. Endangered Species Act (ESA) None
California Endangered Species Act (CESA) None
California Department of Fish and Wildlife None
Bureau of Land Management None
USDA Forest Service None


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