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Alfalfa Butterfly/Orange Sulphur

Colias eurytheme Boisduval, 1852

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Mating pair photo (Click to enlarge)
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Adult ventral photo (Click to enlarge)
Distribution Map
Ohio county distribution
Records by Month
Flight period (Temporal distribution)

STATUS: Naturalized resident; common.

DISTRIBUTION/RANGE: Statewide (see map). This species has been recorded from all 88 counties.

HABITAT: Virtually any open area. This butterfly is especially common in open fields, vacant lots, pastures, and along roadsides. It is most frequent in alfalfa and clover fields.

HOSTPLANT(S): In Ohio, as its common name suggests, this species uses alfalfa as its primary host. It has also been observed ovipositing on yellow hop clover (Xerces Society, 1987). Other legumes are probably utilized as well.

ADULT ENERGY RESOURCES: Alfalfa, red clover, alsike clover, common milkweed, swamp milkweed, self-heal, teasel, peppermint, horseweed, purple coneflower, sunflower, wing-stem, chicory, asters, Canada thistle, ironweed, common boneset, great blue lobelia, and goldenrods. Adults also imbibe moisture from damp soil and mud, and arc often seen in large numbers around puddles in mid-summer.

FLIGHT PERIOD: Many overlapping broods throughout the summer, peaking in early autumn (see graph). Although it is difficult to distinguish from the histogram, there are between three to five generations a year. This is one of the last butterflies to disappear each autumn. Extreme dates range from 10 April to 2 December.

SIMILAR SPECIES: The Clouded Sulphur (Colias philodice). The Sleepy Orange (Eurema nicippe) is superficially similar, but the silver spot in the ventral hindwing cell of C. eurytheme will separate it from E. nicippe.

GENERAL COMMENTS: This species is probably our third most common butterfly after the Cabbage White and the Pearl Crescent. However, C. eurytheme usually becomes the most abundant species in late summer and early autumn. Statewide in occurrence, this species is most frequently encountered with its near relative, C. philodice, in alfalfa and clover fields. often hundreds of adults can be seen flying about in these fields in the summer.

Originally a species of the far west, this species was not part of Ohio's native fauna. Colias eurytheme spread eastward during the 1870's following the widespread cultivation of alfalfa (Shapiro, 1966). The first report of this species in Ohio was in 1874 near Cincinnati (Dury, unpublished notes). It was considered rare in the State (Pilate, 1882; Claypole, 1897; Balcs, 1909; Henninger, 1910) until about 1930 when Baker (unpublished notes) reported it as common in Stark County. This increase in numbers is similar to trends found in other eastern states (Shapiro, 1966). Prior to the widespread cultivation of alfalfa, this species used native legumes as its primary foodplants. Today this butterfly feeds almost exclusively on alfalfa in Ohio and can be a minor pest at times.

The recent range expansion of this species has resulted in contact with C. philodice, and subsequent hybridization between these two species. Despite the prevalence of hybrids throughout Ohio, both butterflies have retained their integrity and must be considered as distinct species (Silberglied and Taylor, 1973).

As is the case with C. philodice, C. eurytheme is also phenotypically variable. In early spring and autumn, adults are smaller and have the orange areas greatly reduced on the dorsal forewing. Summer individuals are larger and usually brighter orange. White females are common, particularly in late summer. In Pennsylvania, white females can represent up to 40% of the autumn population (Shapiro, 1966). Females range from white to buff to orange. Aberrations and somewhat melanic individuals are fairly common.

The flight of C. eurytheme is fairly rapid, slightly erratic, and usually within one meter of the ground. Males patrol back and forth over open fields and hillsides in search of recently emerged receptive females (Paul A. Opler, pers comm, 1989). Colias eurytheme is best observed while the adults are feeding at nectar sources.

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