First placed on the candidate list: 1984
Years waiting for protection: 20
Range: Arizona
Habitat: mountain springs

Stephan’s riffle beetle is a tiny, black aquatic insect that evolved in isolation within a single canyon in low-volume springs and seeps in the Santa Rita Mountains of southern Arizona. The riffle beetle has been listed as a candidate for protection under the Endangered Species Act since 1984. Although the population has since declined to a few individuals and may actually have gone extinct, the Stephan’s riffle beetle is still waiting for endangered species protection.

The beetle is thought to feed on microorganisms such as algae scraped from substrate surfaces and to attach its eggs to the underside of submerged rocks, woody debris or aquatic plants. Upon hatching, the beetle disperses via the single flight of its life and is not known to ever again leave the water.

In the 1930s, the Civilian Conservation Corps channelized into pipes the sole spring where the Stephan’s riffle beetle was located. Runoff from a pipe apparently maintained the population until 1976, when the water was diverted to a developed campground’s water storage tank. In 1984, the beetle became a candidate for Endangered Species Act protection, but no action was taken. Three years later, just three beetles could be found in a small puddle from runoff from the campground tank and in a seep some distance upslope. In a 1993 survey only one Stephan’s riffle beetle was found.

graphic Andrew Rodman ©2002
May 3, 2004
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