Fender's Blue Butterfly

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Fender's Blue Butterfly

Icaricia icarioides fenderi

ListedJanuary 25, 2000
FamilyLycaenidae (Gossamer-winged butterfly)
DescriptionA small butterfly.
HabitatNative prairie.
FoodFeeds only on lupines.
ReproductionLays internally fertilized eggs, which develop into larvae with 5 instars, then a pupal stage, followed by metamorphosis into the adult.
ThreatsHabitat loss.


Fender's blue butterfly is one of about 12 sub-species of the Boisduval's blue butterfly (Icaricia icarioides ), a widespread species of western North America. Fender's blue butterfly is a relatively small species, with a wingspan of about 1.0 in (2.5 cm). The upper wings of the males are colored a brilliant blue, with black borders and basal areas. The upper wings of the females are colored brown. The undersides of the wings of both sexes are creamy tan, with black spots surrounded with a fine halo of white. Male Fender's blue butterflies have relatively small white spots on the undersides of the wings; this is a distinguishing characteristic of the sub-species.


Adult Fender's blue butterflies lay their eggs on species of lupines (Lupinus spp.), which are the food plant of the caterpillars during May and June. Of the 32 sites where Fender's blue butterfly is known to occur, Kincaid's lupine (Lupinus sulphureus kincaidii ) co-occurs as the larval host plant at 27 of the sites. Other species of lupines are secondary host plants at these and other sites. Newly hatched larvae feed for a short time, reaching their second in-star in the early summer, at which point they enter an extended diapause (a state of suspended activity) and eventually overwinter in leaf litter. They become active again when the weather warms sufficiently in the following spring, around March or April. Once the winter diapause is broken, the larvae feed and grow through three to four additional instars, enter the pupal stage, and emerge as adult butterflies in April and May. Overall, a Fender's blue butterfly may complete its life cycle in one year, although this can extend over two calendar years. The larvae of other species of Boisduval's blue butterflies are known to have specialized glands that secrete a sweet solution, which is sought by certain ant species who actively protect the caterpillars from predators and parasites. This mutualism is likely to also occur between ants and larvae of Fender's blue butterfly, although it has not been specifically observed by field biologists.


Fender's blue butterfly inhabits native, dry, upland prairie habitat. The dominant plant species are red fescue (Festuca rubra ) and/or Idaho fescue (Festuca idahoensis ), with indicator species including Tolmie's mariposa (Calochortus tolmiei ), Hooker's catchfly (Silene hookeri ), strawberry (Fragaria virginiana ), rose check-mallow (Sidalcea virgata ), and common lomatium (Lomatium spp.).


Fender's blue butterfly is a locally evolved (or endemic) subspecies that is only known from the Willamette Valley of Oregon. This is a 130-mi (209-km) long and 20-40 mi (32-64 km) wide alluvial floodplain with an overall northward gradient.


The indigenous Kalapooya Indians cleared and burned land used for food gathering and hunting in the Willamette Valley. This activity resulted in the maintenance of extensive areas of grassland in a region capable of supporting forest (a habitat inhospitable to the Fender's blue butterfly). After the beginning of the European settlement in 1848, the amount of burning decreased greatly because settlers suppressed large-scale wildfires. This resulted in the change from predominantly open, park-like communities of the valley basin into dense oak and conifer forests, or into scrub lands following logging. Even more important in terms of ecological change was the rapid conversion of most of the bottomland area of the valley into agricultural land-uses. These various changes resulted in an enormous decrease in the amount of habitat available to support Fender's blue butterfly, and a precipitous decrease in its population (and also those of some associated endemic species). In large part, uncultivated fencerows and intervening strips of land along agricultural fields and roadsides served as the only refugia from these forces of ecological change. In the early 1990s, only about 988 acres (400 hectares) of native upland prairie remained in the Willamette Valley, representing only 0.1% of the former area of this ecosystem type. Within this remnant prairie habitat, Fender's blue butterfly occupies about 32 sites totaling 408 acres (165 hectares).Ongoing threats to the rare butterfly include habitat loss or damage from a wide variety of causes, such as urbanization, agricultural activities (including insecticide spraying), forestry practices, and roadside maintenance (including herbicide spraying). Collecting for the commercial trade in butterflies is also a hazard at some sites.

Conservation and Recovery

Fender's blue butterfly receives no protection under the Oregon Endangered Species Act, which does not include invertebrate animals in the definition of "wildlife." This means that some commercial collecting of the endangered butterfly continues to occur. Conservation of Fender's blue butterfly requires that this collecting be stopped. In addition, most of the surviving habitat occurs on privately owned land. It is crucial that this habitat be protected, which can be done by acquiring the land and establishing ecological reserves, or by negotiating conservation easements or other suitable land-management agreements with the landowners. The U. S. Fish and Wildlife Service has plans to begin to undertake such conservation activities, beginning in the year 2000. Because of the extremely small area of surviving native prairie in the Willamette Valley, it would be prudent to undertake an action in ecological restoration to increase the cover of this community type. This would benefit Fender's blue butterfly as well as other threatened co-occurring species.


U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
(503) 231-6121

U. S. Fish and Wildlife Service
Oregon State Office
2600 SE 98th Ave, Suite 100
Portland, Oregon 97266
Telephone: (503) 231-6179
Fax: (503) 231-6195


U.S. Fish and Wildlife Service. 2000. Endangered and Threatened Wildlife and Plants; Endangered Status for Erigeron decumbens var. decumbens (Willamette Daisy) and Fender's Blue Butterfly (Icaricia icarioides fenderi ) and Threatened Status for Lupinus sulphureus ssp. kincaidii (Kincaid's Lupine). http://www.epa.gov/fedrgstr/EPA-SPECIES/2000/January/Day-25/e1561.htm