Species Fact Sheet Fender's blue butterfly Icaricia icarioides fenderi
STATUS: ENDANGERED CRITICAL HABITAT: DESIGNATED
Fender's blue butterfly potentially occurs in these Oregon counties: Benton, Lane, Linn, Polk, Washington, Yamhill (Map may reflect historical as well as recent sightings)
Fender's blue butterfly was listed as endangered in 2000.
Critical habitat was designated in 2006. This butterfly does not
have a recovery plan.
Historical Status and
This subspecies of the Boisduval's blue butterfly (Icaricia
was believed to be extinct from 1937 until it was rediscovered
in 1989. The distribution of this butterfly is restricted to the
Willamette Valley, Oregon, where it currently occupies 32 sites
in Yamhill, Polk, Benton, and Lane Counties. One population
is found in wet, Deschampsia-type prairie, while all other remaining
populations are found on drier, upland prairies characterized
by Festuca (forage grasses) species. Sites occupied by Fender's
blue butterfly are located almost exclusively on the western side
of the valley, within 33 kilometers (21 miles) of the Willamette
River. The largest populations occur at Baskett Slough National
Wildlife Refuge and at Willow Creek Main Preserve managed by The
Fender's blue butterfly occurs in native prairie habitats. Most Willamette Valley prairies are early seral (one stage in a sequential progression) habitats, requiring natural or human-induced disturbance for their maintenance. The vast majority of these prairies would eventually be forested if left undisturbed. Fender's blue butterfly is typically found in native upland prairies, dominated by red fescue (Festuca rubra) and/or Idaho fescue (F. idahoensis). The butterfly uses three lupine species as larval food plants which include: Kincaid's lupine (Lupinus sulphureus kincaidii), sickle-keeled lupine (L. albicaulis) and spur lupine (L. arbustus). Kincaid's lupine (listed as Threatened), occurs on a few, small prairie remnants in the Willamette Valley. Adult Fender’s blue butterflies use a variety of plants as nectar sources; these include: tapertip onion (Allium acuminatum), narrowleaf onion (Allium amplectens), Tolmie's mariposa lilly (Calochortus tolmiei), small camas (Camassia quamash), clearwater cryptantha (Cryptantha intermedia), wooly sunflower (Eriophyllum lanatum), Oregon geranium (Geranium oreganum), toughleaf iris (Iris tenax), pale flax (Linum angustifolium), blue flax (Linum perenne), Meadow checkermallow (Sidalcea campestris), rose checker-mallow (Sidalcea virgata), bird vetch (Vicia cracca), common vetch (V. sativa), and tiny vetch (V. hirsute).Native plants that occur on native upland prairies serve as herbaceous indicators of prairie condition. These dry, fescue prairies make up the majority of habitat for Fender's blue butterfly. Although Fender's blue butterfly is occasionally found on steep, south-facing slopes and barren rocky cliffs, it does not appear to thrive in the xeric oatgrass communities often found there.
Fender's blue butterfly is a relatively small butterfly with
a wingspan of approximately 2.5 centimeters (1 inch). The upper
wings of the males are brilliant blue with a blackish wing margin
and a white fringe of scales. The upper wings of the females are
brown with a white fringe of scales. The undersides of the wings
of both sexes are creamish-tan with black spots surrounded by a fine,
white border or halo.
The life cycle of a Fender's blue butterfly begins in late spring
or early summer when an adult female deposits an egg on the underside
of a Kincaid's lupine leaflet. The egg soon hatches and the larva
feeds on lupine leaflets. The larva may pass through one molt
before dropping to the ground in mid-June or July where it goes
into hibernation for the fall and winter. In the following March
or April, the larva begins to feed on fresh lupine leaflets again.
After three to four additional molts, it ecloses into a butterfly
in May and begins the cycle again.
Reasons for Decline
Fender's blue butterfly is endangered because native prairie
habitat has been converted to agriculture, subjected to fire suppression,
invaded by non-native plants, or otherwise developed. Refugia
from these forces of change are mostly limited to fence rows and
intervening strips of land along agricultural fields and roadsides.
Even these areas are disappearing now as private landowners come
under increasing pressure to develop.
By nature, prairies are a transient community, requiring disturbance
to prevent a transition to forest. With extensive changes in the
fire regime, disturbances that maintained native prairies have
been substantially altered, allowing tree and shrub species to
invade and shade out low-growing Kincaid's lupine, the species
upon which this butterfly depends. In addition, non-native species
such as Himalayan blackberry (Rubus discolor) aggressively overtake
open spaces and crowd out native species.
Loss of native prairie has resulted in the isolation of butterfly
populations which were once inter-connected. As the number of
sites declines and the distance between them increases, opportunities
for adult movement between populations are reduced. Populations
isolated in this manner face a higher risk of extinction because
they are more vulnerable to natural and human-made disturbances.
Natural processes which functioned to maintain open prairies
have been altered and non-native plant species have invaded most
sites. Historically, large-scale fires played a role in maintaining
prairies in an open state. Fires kept shrubs, trees, and most
non-native species from invading. Today, prairie remnants are
no longer maintained by fire due to suppression efforts. Human
intervention, including management, restoration and protection,
is needed to prevent further loss. Currently, controlled burning,
careful mowing, and hand clearing are used to manage prairie ecosystems.
References and Links
U.S. Fish and Wildlife Service. 2006. Designation of Critical Habitat for the Fender's blue butterfly (Icaricia icarioides fenderi), Lupinus sulphureus ssp. kincaidii (Kincaid's lupine), and Erigeron decumbens var. decumbens (Willamette daisy): Final rule. FR 63861 63977.
U.S. Fish and Wildlife Service. 2000. 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