Nathalis iole
Dainty Sulphur

Family Description:
Alternate Common Name: Dwarf Yellow.
Caterpillar: The caterpillar is small, reaching a maximum length of 5/8 inch. It can vary in color, but generally is light to dark green and striped lengthwise along the back with a purplish or brownish stripe. The sides may be marked with dark brown and/or yellow. The body is covered with short hair. Alternatively, the caterpillar may be solid green with a yellowish head.
Adult: The butterfly is small, with a wingspan of 3/4 to 1 1/4 inches, and varies in its appearance. Generally the upperside is yellow to orangish yellow and heavily marked with brownish black on the tip of the forewing and along the edge where it meets the hindwing. Females have more black than males, and their wings may be edged with black as well. Underneath, the forewing is yellowish orange towards the body and faded black towards the tip; there may be several black spots near the outside edge. The underside of the hindwing is yellowish in summer individuals and greenish brown in winter individuals.

This species is a yearlong resident of the extreme southern U.S., from southernmost California to Florida, and Mexico. In the spring and summer, adults migrate north throughout most of the U.S. into Canada, primarily in the Great Plains. In Idaho, it has been documented to occur in three counties: Ada, Canyon, and Franklin.

It occurs in open, often drier areas, such as fields, grasslands, and disturbed areas, and along corridors such as rivers, railroads, and roadsides.


Caterpillar: Caterpillars feed on flowers belonging to the sunflower family (Asteraceae) including sneezeweed (Helenium spp.), bur marigold (Bidens pilosa), cultivated marigold (Tagetes spp.), and fetid marigold (Dyssodia spp.).
Adult: Butterflies drink flower nectar.

There are continuous generations of caterpillars where the species occurs year-round. Scientists have not yet confirmed whether the northward migration is either accomplished by individual adults or by successive generations of adults. No stage is believed to be capable of enduring winter frosts; individuals occurring in the north when summer ends die.

Males patrol near the ground in search of receptive females. Females lay eggs singly on the leaves of young host plants.

Idaho Status: Unprotected nongame species.
Global Rank:

G5; populations are widespread, abundant, and secure.

Ferris, C. D. and F. M. Brown. (eds.) 1981. Butterflies of the Rocky Mountain States. Univ. of Oklahoma Press, Norman, Oklahoma, USA, 442 pp.

Opler, P. A., H. Pavulaan, and R. E. Stanford. 1995. Butterflies of North America. Jamestown, North Dakota, USA: Northern Prairie Wildlife Research Center Home Page. (Version 05Nov98).

Opler, P. A. and A. B.Wright. 1999. A Field Guide to the Western Butterflies.   Second Edition.  Peterson Field Guide Series. Houghton Mifflin Company, New York, New York, USA, 540 pp.

Pyle, R. M. 1981. National Audubon Society Field Guide to North American Butterflies. Alfred A. Knopf, Inc., New York, New York, USA, 924 pp.

Scott, J. A. 1986. The Butterflies of North America. Stanford University Press, Stanford, California, USA, 583 pp.

Stanford, R. E. and P. A. Opler. 1993. Atlas of Western U.S.A. Butterflies (Including Adjacent Parts of Canada and Mexico). Published by authors, Denver, Colorado, USA, 275 pp.