Reakirt's Blue (Hemiargus isola [Reakirt])
Wing span: 3/4 - 1 1/8 inches (2 - 2.9 cm).
Identification: Upperside of male light blue with darker veins and dusky border; female darker. Underside of forewing with postmedian row of 5 round black spots circled with white.
Life history: Males patrol for females with an erratic flight during daytime. Females lay eggs singly on flower buds of host during midday. Caterpillars eat flowers and seedpods, sometimes leaves; and are tended by ants which presumably protect the caterpillars in return for their sugary secretions.
Flight: All year in South Texas; 3 broods from March-November in the remainder of its residential range; migrates north once each year after hibernating in the south.
Caterpillar hosts: Many plants in the pea family (Fabaceae) including yellow sweet clover (Melilotus officinalis), rattleweed (Astragalus), mesquite (Prosopis), indigo bush (Dalea), mimosa (Albizia), and indigo (Indigofera) species.
Adult food: Flower nectar from a variety of herbs including spearmint and white sweet clover.
Habitat: Grasslands, fields, desert, meadows, weedy areas, creeksides.
Range: Resident from southern California, the Southwest, and Texas through Mexico and Central America to Costa Rica. Summer migrant north and east through the Mississippi River states to Wisconsin and Ohio.
Conservation: Not required.
The Nature Conservancy Global Rank: G5 - Demonstrably secure globally, though it may be quite rare in parts of its range, especially at the periphery.
Management needs: None reported.
Opler, P. A. and G. O. Krizek. 1984. Butterflies east of the Great Plains. Johns Hopkins University Press, Baltimore. 294 pages, 54 color plates. Opler, P. A. and V. Malikul. 1992. A field guide to eastern butterflies. Peterson field guide #4. Houghton-Mifflin Co., Boston. 396 pages, 48 color plates. Scott, J. A. 1986. The butterflies of North America. Stanford University Press, Stanford, Calif. 583 pages, 64 color plates. Tilden, J. W. 1986. A field guide to western butterflies. Houghton-Mifflin Co., Boston, Mass. 370 pages, 23 color plates.
Author: Jane M. Struttmann
State and Regional References:
Opler, Paul A. 1999. Peterson Field Guide to Western Butterflies, revised edition. Houghton Mifflin Co., Boston, Mass. Stanford, R.E. and P.A. Opler. 1993. Atlas of Western USA Butterflies. Privately published, Denver, Colo.