Cosmopterix montisella

Distinguished from congeners by combination of: four white streaks in forewing basal area (subcostal strongly bending from costa and widening distally); broad orange-brown transverse fascia beyond middle with tubercular silver or pale golden metallic borders; dorsal metallic spot approximately twice size of costal spot and much closer to base; broad white costal streak originating from costal spot. Variable characters include length and shape of white basal streaks and degree of interruption of apical metallic line. Male and female externally similar.

Small moth with forewings 5.1–6.5 mm. Head: frons pale ochreous with greenish and reddish reflections; vertex and neck tufts dark bronze brown with greenish and reddish gloss, edged white laterally and medially; collar dark bronze brown. Labial palpus with first segment short and ochreous, second segment four-fifths length of third and dark brown with white longitudinal lines, third segment white with dark brown lateral lines. Antenna dark brown with variable white markings from base. Thorax and tegulae dark bronze brown with greenish and reddish gloss; thorax with white median line, tegulae lined white inwardly. Legs dark brown with reddish gloss; foreleg femur grey, midleg and hindleg femora pale golden; foreleg tibia and tarsal segments one and two with white line; midleg and hindleg tibiae with white oblique basal and medial lines and white apical rings. Forewing dark bronze brown with reddish golden gloss, bearing four white streaks in basal area (subcostal from base to one-quarter bending from costa and widening distally, short medial ending at or beyond subcostal, subdorsal slightly longer than medial, narrow dorsal from beyond base to one-seventh); broad orange-brown transverse fascia beyond middle, at costa twice width of dorsum; inner edge bordered by broad tubercular silver or pale golden metallic fascia widening towards dorsum; outer edge bordered by two tubercular silver or pale golden metallic costal and dorsal spots (dorsal spot twice size of costal, closer to base); broad white costal streak from costal spot; pale golden to golden metallic apical line on dorsum, often interrupted, becoming broad white streak in apical cilia. Cilia dark bronze brown around apex, ochreous-brown on dorsum towards base. Hindwing brownish-grey with ochreous-brown cilia. Abdomen dorsally brownish yellow, laterally and ventrally dark grey with broad white posterior bands on segments; anal tuft ochreous-white dorsally, mixed brown ventrally.

United States: from New York and Oregon south to New Mexico, Arizona and California. Disjunct records from Arkansas, Iowa, and Vermont. Established in Michigan.

Adults active early June to mid-September where univoltine. In southern Arizona, bivoltine with adults in July, August, and late September.

Univoltine throughout much of range; bivoltine in southern Arizona.

• small moth
• metallic coloration
• North American
• voltinism variation

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life