Coelodasys unicornis (J.E. Smith, 1797)
Unicorn Caterpillar Moth
View Photographic Plate
WA : Lewis Co.
Lewis & Clark SP, 449 ft
June 30, 1990, L. G. Crabo.
Specimen courtesy of LGCC
Photograph copyright: Merrill A. Peterson
Coelodasys unicornis is our smallest Coelodasys species (FW length 14–17 mm). It has a relatively short and stubby forewings with a prominent light reddish area at the outer margin and a fairly "busy" pattern of lines, streaks, and colorful mottling. The forewings are gray or mixed gray and red-brown medial to the postmedial line and light red-brown, blue-gray, black, and gray distal to this line. The scalloped transversely oriented postmedial line, black bar-like discal spot usually preceded by a pale gray area in the cell, and a series of black and black and white dashes between veins on the distal area are the most prominent marks. A double black basal line separates a small pale basal area from the rest of the forewing. The male hindwing is light gray, usually with extensive gray shading and marginal band. The female hindwing is darker gray. The thorax is light to medium gray, with dark barring on the collar and weak tufts at the posterior margin. The male antenna is bipectinate while that of the female is simple.
Specimens from western Washington and Oregon are lighter, more reddish in color, and have a more mottled appearance than those from further east in our region.
Coelodasys unicornis is closest in appearance to Coelodasys conspecta, until recently considered to be one of its synonyms (Lafontaine & Schmidt 2010) (see C. conspecta for further discussion). Coelodasys conspecta is less mottled, has a luteous or pale gray pale distal forewing, not reddish as in C. unicornis, and has a whiter male hindwing than C. unicornis.
This species is placed in the genus Coelodasys Packard in a recent check list of the prominents of the New World by Becker (2014), having previously been placed in the genus Schizura Doubleday.
Larva is mostly smooth, green and mottled gray and red with a sharp thoracic dorsal hump. It is illustrated by Miller & Hammond (2003).
This species is common in hardwood forests and riparian zones throughout North America. In the Pacific Northwest, these habitats include urban areas, coastal rainforests, mixed hardwood forests at low elevations west of the Cascades, montane hardwood-conifer forests, and riparian zones east of the Cascades.
Coelodasys unicornis is found in mesic forests throughout our region.
This species has a broad distribution in North America. Forbes (1948) gives its range from Nova Scotia to Florida along the east coast. It probably occurs widely through the West, although the exact range is uncertain due to confusion with C. conspecta.
This species is a generalist feeder on many kinds of hardwood trees and shrubs, particularly in the families Fagaceae, Betulaceae, Rosaceae, and Ericaceae. Larvae are sometimes pests in fruit orchards.
Aduls have a very long flight season suggesting that it might be multiple brooded. They have been collected from late May until mid September. They are nocturnal and come to light.
Larvae are sometimes pests in fruit orchards and urban gardens.
Lafontaine & Schmidt (2010)
Miller & Hammond (2003)
Powell & Opler (2009)