Reakirt's Blue - Echinargus isola
[From Ferris and Brown 1981; Scott 1986; Opler and Wright 1999; Glassberg 2001; Pyle 2002] Forewing 1.0-1.2 cm. Lower forewing margin looks clipped. Uppersurface of male blue, of female dusky with blue basally; both sexes with two or three dark spots on trailing margin of hindwing (in anal angle). Undersurface of forewing with arced postmedian row of five or six prominent black spots ringed with white, hindwing with smaller gray and white spots, bars, chevrons, with black and silver spots (two small, one large) in anal angle and sometimes with pale orangish halos.
Many flights; all year in Texas, April to October in California, mid-May to October in Colorado, April to September in Illinois (Scott 1986). Mainly March to October (Glassberg 2001).
Best determined by combination of the uppersurface of both sexes with two or three dark spots on trailing margin of hindwing (in anal angle); undersurface of forewing with arced postmedian row of five or six prominent black spots ringed with white, hindwing with black and silver spots (two small, one large) in anal angle and sometimes with pale orangish halos.
Resident in southwestern US from southern California, southern Arizona and New Mexico, southern Texas, south through Mexico to Costa Rica. Vagrant north to Washington, Idaho, Saskatchewan, upper Midwest in southern Great Lakes region, east to Mississippi River region (Opler and Wright 1999); to 3110 m elevation in southern Rocky Mountain states (Brown 1957; Ferris and Brown 1981); 1311 m to 3805 m elevation in Colorado but mostly below 2804 m (Scott and Scott 1978), 2134 m to at least 2896 m elevation in Wyoming (Nabokov 1953). In Montana, no reports through 1993 (Kohler 1980; Shepard and Opler 1993), but reported since in Silver Bow County (no details available; reported as recently as 2013 in Natrona County, Wyoming). Common to abundant from Texas to Arizona, uncommon to common elsewhere (southern Nevada and Utah, Colorado, Nebraska), vagrant northward (Glassberg 2001).
Migratory; annually moving northward from northern edge of resident range in Texas, New Mexico, Arizona, southern California (Scott 1986; Pyle 2002).
Open areas, weedy fields, pastures, desert thorn-scrub, waste ground, vacant lots, watercourses, moist meadows, mud flats, open woodlands, "hot hillsides" (Nabokov 1953; Emmel 1964; Scott 1986; Opler and Wright 1999; Glassberg 2001; Pyle 2002). Habitat in Montana not described but probably similar.
Larval food plants include Acacia, Albizzia, Amorpha, Astragalus, Coronilla, Dalea, Desmanthus, Glycyrrhiza, Indigofera, Lotus, Medicago, Melilotus, Mimosa, Oxytropis, Prosopis, Rhynchosia, and Trifolium (Ferris and Brown 1981; Scott 1986, 1992, 2006). Adults feed on flower nectar (including Achillea, Astragalus, Berteroa, Chrysothamnus, Cirsium, Eriogonum, Glycyrrhiza, Gutierrezia, Helianthus, Heterotheca, Humulus, Hymenopappus, Hymenoxys, Lavandula, Lesquerella, Liatris, Limonium, Lupinus, Medicago, Melilotus, Mertensia, Nepeta, Perovskia, Polygonum, Psoralea, Rhus, Rorippa, Sedum, Solidago, Sphaeralcea, Symphyotrichium, Tagates, Thlaspi, Trifolium) and mud (Scott 1986, 2014).
Females lay eggs singly on host plant flower buds. Limited information on larval development. Larvae eat host plant flower buds, flowers, fruits, sometimes young leaves, build no nest, are tended by ants (Tapinoma reported in Colorado), exhibit no diapause (overwintering) at any stage in captivity, adults eclose (emerge from pupae) in about 10 days in captivity (Scott 1986, 1992, 2006). Males patrol erratically throughout the day over flats and in meadows near larval host plant in search of females (Scott 1975b, 1986).
- Literature Cited AboveLegend: View Online Publication
- Brown, F.M. 1957. Colorado Butterflies. Proceedings; Numbers Three through Seven. Denver Museum of Natural History, Denver, Co.
- Emmel, T.C. 1964. The ecology and distribution of butterflies in a montane community near Florissant, Colorado. American Midland Naturalist 72(2): 358-373.
- Ferris, C.D. and F.M. Brown (eds). 1981. Butterflies of the Rocky Mountains. Univ. of Oklahoma Press. Norman. 442 pp.
- Glassberg, J. 2001. Butterflies through Binoculars: A Field Guide to the Butterflies of Western North America. Oxford University Press.
- Kohler, S. 1980. Checklist of Montana Butterflies (Rhopalocera). Journal of the Lepidopterists' Society 34(1): 1-19.
- Nabokov, V. 1953. Butterfly collecting in Wyoming, 1952. The Lepidopterists' News 7(2): 49-52.
- Opler, P.A. and A.B. Wright. 1999. A field guide to western butterflies. Second edition. Peterson Field Guides. Houghton Mifflin Company, Boston, Massachusetts. 540 pp.
- Pyle, R.M. 2002. The butterflies of Cascadia: a field guide to all the species of Washington, Oregon, and surrounding territories. Seattle Audubon Society, Seattle, Washington. 420 pp.
- Scott, J.A. 1975b. Mate-locating behavior of western North American butterflies. Journal of Research on the Lepidoptera 14:1-40.
- Scott, J.A. 1986. The butterflies of North America: a natural history and field guide. Stanford University Press, Stanford, California.
- Scott, J.A. 1992. Hostplant records for butterflies and skippers (mostly from Colorado) 1959-1992, with new life histories and notes on oviposition, immatures, and ecology. Papilio new series #6. 185 p.
- Scott, J.A. 2006. Butterfly hostplant records, 1992-2005, with a treatise on the evolution of Erynnis, and a note on new terminology for mate-locating behavior. Papilio new series #14. 74 p.
- Scott, J.A. 2014. Lepidoptera of North America 13. Flower visitation by Colorado butterflies (40,615 records) with a review of the literature on pollination of Colorado plants and butterfly attraction (Lepidoptera: Hersperioidea and Papilionoidea). Contributions of the C.P. Gillette Museum of Arthopod Diversity. Fort Collins, CO: Colorado State University. 190 p.
- Scott, J.A. and G.R. Scott. 1978. Ecology and distribution of the butterflies of southern central Colorado. Journal of Research on the Lepidoptera 17(2): 73-128.
- Stanford, R.E. and P.A. Opler. 1993. Atlas of western USA butterflies: including adjacent parts of Canada and Mexico. Unpubl. Report. Denver and Fort Collins, Colorado 275 pp.
- Additional ReferencesLegend: View Online Publication
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- Allen, T.J., J.P. Brock, and J. Glassberg. 2005. Caterpillars in the field and garden: a field guide to the butterfly caterpillars of North America. Oxford University Press.
- Brock, J.P. and K. Kaufman. 2003. Kaufman Field Guide to Butterflies of North America. Houghton Mifflin Company, New York, NY 284 pp.
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