Fender's Blue Butterfly
Icaricia icarioides fenderi
Status: Endangered
Date Listed: January 25, 2000
Threats: The main threats include habitat fragmentation due to urban and agricultural development, alien species, and fire suppression. 
Description
  • Taxonomic: This tiny butterfly belongs to a group called Blues or Gossamer-winged butterflies in the family Lycaenidae.  Fender’s blue butterfly is one of a dozen unique subspecies of Bosisduval’s blue (Icaricia icarioides).  It is considered a distinct taxon found only in the upland prairies of the Willamette Valley in Oregon. 
  • Physical: Not much bigger than a quarter, the wingspan of Fender’s blue is only 1 inch wide (2.5cm).  Adult males flash a brilliant blue with black boarders on the upper-side of their wings, whereas adult females are an inconspicuous, rusty-brown.  The under-sides of both males and females are a cream-tan with black spots surrounded with fine white halos.  Similar butterfly species include the Pembia blue (Icaricia icarioides spp. pembia) and Puget blue (Icaricia icarioides spp. blackmorei).  The caterpillars are small, solid green and appear humped in profile.  
  • Life cycle: In May, adults lay their eggs on the leaves of Kincaid's Lupine (Lupinus sulphureus ssp. kincaidii), the butterfly's primary host plant.  Larvae hatch and eat lupine until the plant reaches senesces.  At this time (usually in late June), the caterpillars drop to the base of Kincaid's lupine and enter diapause. The caterpillars will remain tucked under the leaf litter until February/March of the following year.  Hungry after their long sleep, they feed again on lupine in order to shed skin and grow big enough to pupate.  They then form cocoons, transform, and emerge as creatures of flight (May).  Fender's blue completes its lifecycle in one year. 
Larval Host Plant: Kincaid's lupine is the preferred host of Fender's blue butterfly, although its caterpillars have been observed on alternate food sources such as the Sickle keeled lupine (Lupinus albicaulis) and the Spurred lupine (Lupinus laxiflorus).  Kincaid's lupine co-occurs in 27 out of the 32 sites where Fender's blue is found (EPA Federal Register Document, January 25,2000).

Range: Fender's blue is endemic to Willamette Valley upland prairies of Oregon.  This means that it is found nowhere else in the world and depends on these upland prairies- a habitat that is rapidly decreasing- for its sole survival.  This geographic area contains two remnant prairies types- upland and wetland prairies.  Current estimates of the remaining native, upland prairie area in the Willamette Valley are less than 400 hectares, less than one-tenth of 1% percent of their original range.  (EPA Federal Register Document, Jan. 25, 2000).  The Willamette Valley is home to approximately 70% of Oregon's human population.  

Habitat:  The Willamette Valley contains a mosaic of habitats including grasslands, woodlands, and forest communities.  As a distinct but remnant habitat, upland prairies are characterized by well-drained soils and a mosaic of perennial grasses and forbs. Upland prairie plant species include bunch grasses such as Idaho fescue (Festuca idahoensis var.roemeri) and low-growing, showy perennial forbs.  Existing upland prairies currently provide habitat for nine plant species of federal, state, and proposed listing status. These habitats are fire dependent, as they were historically burned by the Kalapooya Indians.  Agricultural conversion and fire suppression have severely limited the range of these early seral, dry grasslands (EPA Federal register Document, January 25,2000).  
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