The Trinity bristle snail (Monadenia setosa ) is a species of medium-sized land snail, a terrestrial pulmonate gastropod mollusc in the family Monadeniidae.
The Trinity bristle snail attains a body length of approximately 2.5 cm. It is brown or chestnut-colored and covered with minuscule, translucent bristles, which give the species its common name.
This species is endemic to California. This snail is found in northwestern Trinity County, along the Trinity River, up some of its tributaries and into the Corral Bottom area. It has a healthy population within its territory. It likes cool, wet, shady riparian zones, and prefers areas with a deciduous understory.
The Trinity bristle snail is dependent on cool, moist conditions, and therefore it is only active at night. It spends warmer parts of the day stuck to shady areas on tree trunks, and in especially warm parts of the summer it may not move for days. When conditions are cool enough it feeds on lichen and the tender parts of green plants. The snail has a lifespan of over ten years, and may not reach full size for nearly that long. It is subject to predation by beetles and possibly rodents.
