Orange Sulfur (Colias eurytheme)
Orange Sulfur Colias eurytheme Iowa
Orange Sulfur Colias eurytheme Iowa
(Top) An Orange Sulfur butterfly (Colias eurytheme) on a Western Sunflower (Helianthus occidentalis) at Geode State Park in Iowa.

(Below) The white variation of a female Orange Sulfur or Clouded Sulfur (Colias philodice) at Big Hollow Recreation Area in Des Moines County, Iowa. Because of similarities in the species, this specimen can not be identified.

Details: 

(Top)  Canon EOS 10D,  shutter 1/125 second, aperture f9.5, ISO 100, Canon EF 100 mm macro lens, Canon MR-14EX flash.

(Bottom)  Canon EOS 10D,  shutter 1/200 second, aperture f16, ISO 400, Canon EF 100 mm macro lens, Canon MR-14EX flash.
 

Selected References:

Brock Jim P., Kaufman Kenn. Butterflies of North America. New York: Houghton Mifflin Company, 2003. P 60-61.

Struttmann Jane M. USGS Northern Prairie Wildlife Research Center. "Orange Sulfur (Colias eurytheme)." Butterflies of North America / Butterflies of Iowa. <http://www.npwrc.usgs.gov/resource/distr/lepid/bflyusa/ia/728.htm > (15 Sep. 2004).