The western threadsnake, Leptotyphlops humilis, is native to the southwestern United States and Mexico. In Utah, the western threadsnake occurs only in the extreme southwestern corner of the state, in Washington County.
The western threadsnake is a secretive burrowing species, often living in moist loose soil. Because the species spends so much time under the ground, the western threadsnake's eyes are vestigial, meaning that they no longer function. The western threadsnake eats small invertebrates, such as spiders, insects, and centipedes, and insect larvae. Females lay a clutch of two to six eggs in later summer, and then stay with the eggs until after hatching. The species is nocturnal - individuals are only active on the surface at night.