Ottawa (Dunrobin), ON Canada

9 August 2004   10:17PM EST  (top)
12 June 2003   10:34PM EST  (bottom)

Members of the Geometrinae subfamily of Geometridae are often called the Emeralds, or emerald moths, because so many of the species are green in color.  Dichorda iridaria is one of eight species of Emerald recorded from the Ottawa area (J.D. Lafontaine, pers. comm., 2001), of which six are illustrated on this web site.  Distinguishing between some similar species in this group is often problematic, and in checking my identifications and revising my web pages for this group of moths, I have relied heavily on the work of the late Dr. Douglas C. Ferguson (Ferguson, Douglas C., in Dominick, R.B., et al., 1985, The Moths of America North of Mexico, Fasc. 18.1, Geometroidea: Geometridae (in part)).

Dichorda iridaria has bright green wings, rather more vivid than the other species of Geometrinae seen at my location.  The forewing has prominent, wide white antemedial and postmedial lines; the hindwing has a similar postmedial line but no antemedial line.  In the median, the green is usually suffused with white, especially in the upper half of the wing towards the costa.  Outside the postmedial line, diffuse white rays mark many of the veins on both forewing and hindwing.  Small black discal dots are visible on both wings.  The fringe is greenish white.  On the forewing, the costa is white, speckled with brown, especially near the base of the wing.  Ferguson (1985) indicates a wing length ranging from 11.5 to 15.0 mm in males, and from 15 to 16 mm in females, making this the largest of the Emeralds seen at my location.

According to Ferguson (1985), the host plant for Dichorda iridaria is sumac. Handfield (1999) indicates two generations per year for my general area, with adult flight seasons from late May into early July, and from the last few days of July into the second half of August.

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