Prairie Species Habitat Conservation Plan – Fender’s Blue Butterfly

Icaricia icarioides fenderi

​​Status

Fender’s Blue butterfly was listed as an endangered species under the federal Endangered Species Act in 2000. Fender’s Blue was actually thought to be extinct from about 1940 until the late 1980s, when biologists discovered a few remaining populations on prairie remnants in the Willamette Valley.

Description

Fender’s Blue butterfly is a member of the Lycaenidae family, and is in the Polyommatinae (blue butterfly) sub-family. Fender’s Blue is a small butterfly with an approximately 1 inch wingspan. Upper wings are blue in males, and brown in females. The underside of both gender’s wings are creamy tan with two rows of black spots and a white border.

Range and Habitat

This sub-species occurs in upland prairie or wet prairie habitats. Fender’s Blue is currently found in five counties in Oregon: Linn, Lane, Benton, Yamhill, and Polk County.

Two critical elements of Fender’s Blue butterfly habitat are larval host plants and nectar plant species. Kincaid’s lupine (Lupinus sulphureus ssp. kincaidii) is the primary larval host plant for Fender’s Blue butterfly. Secondary host plants include sickle-keeled lupine (Lupinus albicaulis) and spur lupine (Lupinus arbustus).

Adult butterflies lay their eggs on lupine leaves in May and June, and larvae (caterpillars) hatch out a few weeks later. The larvae feed for a few weeks, then go into diapause (similar to dormancy) at the base of the plant until the following February or March. Emerging larvae then feed on young lupine leaves and inflorescences. The larvae grow and develop quickly, pupate, and emerge as butterflies in early May.

Adult butterflies feed on nectar (sugary fluid) produced by certain flower species. Nectar species to support Fender’s Blue include narrowleaf onion (Allium amplectens), Tolmie startulip (Calochortus tolmiei), common camas (Camassia quamash), dwarf checkermallow (Sidalcea virgata), and Oregon sunshine (Eriophyllum lanatum), among others. Insufficient nectar sources may limit Fender’s Blue population size.

Threats

Remaining populations of Fender’s Blue are at risk from:

• Further habitat loss or fragmentation
• Invasion of prairie habitats by non-native species
• Loss of larval host plants
• Encroachment of trees and shrubs into prairie habitats
• Elimination of natural disturbance regimes