Ottawa (Dunrobin), ON Canada

13 July 2005   9:51PM EST  (top left)
7 July 2005   10:44PM EST  (top right)
3 July 2005   12:01AM EST  (bottom left)
30 June 2005   11:43PM EST  (bottom right)

Polia nimbosa, sometimes called the Stormy Arches moth, is one of several species of Polia recorded from the Ottawa area (J.D. Lafontaine, pers. comm., 2001), three of which are illustrated on this website.

Polia nimbosa has a whitish to pale gray forewing, mottled in gray to black.  The orbicular, claviform and reniform spots have sharp black outlines.  The basal, antemedial and postmedial lines are double, scalloped, and variably distinct; the lines are much clearer in the top left photo than in the top right photo.  The subterminal line is jagged rather than scalloped, and even when it is indistinct, there is usually a small sharp black mark near the anal angle.  There is dark gray shading near the costa, darkest between the orbicular and reniform spots; some specimens also have dark shading in the median next to the inner margin.  The hindwing is grayish brown; a grayish median line originates near the anal angle and is bordered with pale brownish gray along its outer edge.  Covell (1984) indicates a wingspan of 4.0 to 6.5 cm for this species. 

According to Handfield (1999), the host plants for Polia nimbosa are reported to include alder, huckleberry, gooseberry and currant species, maple and several other woody trees and shrubs. For my general area, he indicates an adult flight season from the later part of June through the first ten days of August.

My records to date for Polia nimbosa (each date representing "the night of") are in the table below: