Species Polia nimbosa - Stormy Arches - Hodges#10275

10275

NIMBOSA: from the Latin "nimbus" (rain cloud; storm cloud); probably refers to the dark mottling on the forewing, reminiscent of the color of a storm cloud, and the origin of the common name Stormy Arches

locally common

wingspan 40-65 mm

Adult: tegulae ("shoulder pads" on thorax) pale with black margins; forewing pale gray, mottled with gray and black; orbicular, claviform, and reniform spots with sharp black outlines; reniform spot strongly curved; AM and PM lines double, scalloped; PM line resembles a sinuous series of connected white chevrons; ST line jagged, and has two small black spots near anal angle (the spots are either side-by-side or joined, and are a distinctive feature) - see excellent image taken from All-Leps site here

hindwing grayish or brownish; median line, originating near anal angle, bordered distally by pale band, followed by dark band along outer margin

coast to coast in northern United States and southern Canada (Newfoundland to North Carolina, west to northern California, north to British Columbia)

adults fly from June to August

larvae feed on leaves of alder, birch, gooseberry (Ribes spp.), huckleberry (Gaylussacia spp.), maple, willow

one generation per year

Cloudy Arches (Polia imbrifera) forewing has a less distinct PM line, a more noticeable whitish ST line, and a relatively large triangular dark patch near anal angle (rather than two small black dots set side-by-side, as in P. nimbosa)

Polia propodea has dark "shoulder pads" (tegulae), a darker gray forewing with a distinct blackish ST line, and two tiny white spots in lower corner of reniform spot - lacking in P. nimbosa

(compare images of all three species at CBIF)

live adult images plus description, food plants, flight season (Lynn Scott, Ontario)

pinned adult image (CBIF)

pinned adult image by John Glaser, plus food plants (Larry Line, Maryland)

pinned adult images of male and female (James Adams, Dalton State College, Georgia)

pinned adult images (All-Leps)

food plants; PDF doc plus flight season, life cycle (Macrolepidoptera of Mont Saint-Hilaire Region, McGill U., Quebec)

presence in North Carolina; PDF doc list (Southern Lepidopterists Society)

presence in California; list (U. of California at Berkeley)

distribution in Canada list of provinces (U. of Alberta, using CBIF data)