The Fender’s blue is tiny — only about an inch across — and endangered, a butterfly found only in the Willamette Valley of northwestern Oregon. First noticed in the 1920s, it wasn’t scientifically documented and named until 1931. Biologist Ralph Macy named it for his friend Kenneth Fender, an entomologist and mail carrier. Later in the 1930s, the species was presumed extinct, but small populations were rediscovered in 1989. Fender’s blue butterflies are completely dependent upon the threatened Kincaid's lupine. Fender’s blues lay one egg at a time on the back of a Kincaid's lupine leaf, each egg no larger than the head of a pin. Climate change may change the availability of this butterfly’s host and nectar plants and disrupt the synchrony of the butterfly life cycle with its host plants.

In January 2000, the Fender's blue was added to the endangered species list by the U.S. Fish and Wildlife Service; the Center secured critical habitat for the rare species in 2006.