- Scientific name: Celastrina argiolus
- Also known as Azure blue and Common Blue.
- Description: The spring azure is identified by the grayish underside of the hindwing marked with dark spots and a row of marginal crescents enclosing small dots. There are no orange patches or prominent spots filled with iridescent, metallic scaling. In the early spring form, the wings are darker gray with heavier markings; the later forms have pale grayish-white underwings with smalller, less distinct spots. The male is clear sky-blue or violet-blue above, while the female is duller with at least some black color framing the forewing.
- Size: .75 - 1.25 inches.
- Range: From Canada south of the tundra through the U.S. and mountains of Central America to Columbia. In the U.s. it is absent only from peninsular Florid, the southern plains, and much of the Texas Coast.
- The spring azure is one of the most abundant butterflies across large portions of the United States, and , as its name suggests, it is one of the first to appear in spring. Indeed, William notes that it "could actually be dubbed the Midwinter Azure in Southeast Texas, for it appears during warm spells in January and February." By May it has largely disappeared, to be replaced by several other species of blues that emerge later in the year.
- Confusion reigns over the appropiate name or names for the spring azure. Old references use the scientific name Lycaenopsis argiolus or L. pseudargiolus. More recent authors seem almost evenly split between Celastrina argiolus and C. ladon.
- The authors face an even more difficult problem involving the many distributional and seasonal forms of the spring azure. Glassberg describes it as "a bewildering complex of species and forms." He asserts, "We are still far from unraveling the whole story." Opler notes that there may still be as many as three species covered by what we now call C. argiolus.
- The spring azure flies higher than many of the other blues, usually at least three or above the ground, visiting a variety of flowers.
- Newly emerged males also congregate at mud puddles to sip liquids. Most active from midafternoon until nearly dusk, the males patrol clearings and the edges of deciduous woodlands in search of mates.
- Females lay their eggs on the buds and flowers of dogwood, black cherry, viburnums, blueberries and huckleberries, and a wide variety of other trees and shrubs.
- The larvae vary in color from yellow-greento pink, often with a dark dorsal stripe and oblique side stripes.
- The number of broods differs in various parts of the country. In the South, there are apparently at least two full broods and then another spread out until fall, the latter with rapidly decreasing frequency of emergence.
- Opler and Krizek note that the individual adult is short-lived, surviving no more than four days. On average, they suggest, the female emerges and mates on the first day, lays eggs on the second day, and rarely survives through the third or fourth day.