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The Fender’s Blue Butterfly, once thought to be extinct, was rediscovered in 1989. In 2000, it was listed as an endangered species under the Endangered Species Act. They are small, with a wingspan of only 2.5 centimeters, or 1 inch. The male’s upper wings are bright blue with black borders; the female’s upper wings are completely brown. The under wings of both sexes are cream with black spots outlined in white. Habitat destruction is the number one cause of the decline of the Fender’s Blue population. The primary host plant for the Fender’s Blue larvae is the Kincaid’s Lupine which is also listed as endangered. Less than one tenth of a percent of the upland and wetland prairies exist from the time the settlers came to the Willamette Valley in the 1800’s. Without swift human intervention, the rare wetland habitats and the Fender’s Blue may not exist for much longer.


It is often difficult to tell the difference between the butterflies when they are in flight. The one on the left is the male and the one on the right is the female. You can tell by the brown upper wings on the female. The male's upper wings are always bright blue.

The Life Cycle of the Fender's Blue Butterfly

Here is a Fender's Blue on its larval host plant, the Kincaid's lupine.

Stage One
The adult female lays her eggs on the relevant food plant and larval host plant. (Kincaid’s lupine)

Stage Two
Around 5 days later, a tiny caterpillar larva will hatch. It gets busy eating and shedding its skin.

Stage Three
After the larva molts four times, the skin removed reveals the chrysalis or pupa (like the hard shell of a cocoon). Inside the pupa the caterpillar is maturing into a butterfly.

Stage Four
When the caterpillar is matured, it has become an adult butterfly that lays eggs and reproduces. Within about five days the butterfly will die.