Ottawa (Dunrobin), ON Canada

5 June 2003   11:28PM EST  (top)
9 June 2005   11:24PM EST  (second from top)
19 May 2003   10:01PM EST  (third row, left)
8 June 2003   9:12PM EST  (third row, right)
2 June 2005   12:56AM EST  (fourth row, left)
29 May 2005   9:09PM EST  (fourth row, right)
9 June 2005, 10:39PM EST  (fifth row, left)
25 May 2005   10:51PM EST  (fifth row, right)
20 May 2003   6:12AM EST  (bottom row, left)
6 June 2004   9:39PM EST  (bottom row, right)

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.  Hethemia pistasciaria 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 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)).

The Pistaschio Emerald, Hethemia pistasciaria , is named for the color of the male moth, which has wings of pistaschio green to bright olive on the dorsal or top side.  The female has sage green wings, similar to a day-flying species of Emerald that I have not yet observed.  The antemedial and postmedial lines are fine, whitish, and somewhat wavy; in some specimens the lines are reduced to tiny white dashes at the veins.  In fresh specimens, the am and pm lines may be bordered by slightly darker green shading on the medial side.  In many of the specimens I have observed, the costa is bordered with a brownish color; Ferguson (1985) describes this costal coloration as pinkish or purplish brown in males, green or brown in females.  The outer margin of the hindwing angles to a point.  The fringe in fresh specimens is brownish in males, and green in females, although Ferguson notes some differences with specimens from some more southerly locations.  The underside of the wings of the male moth is bright ochre yellow (bottom left photo), even when the upper side of the wings is green.  According to Ferguson, the wing length ranges from 8.5 to 10.5 mm in males, and 10 to 13 mm in females.

Ferguson (1985) comments in some detail about the instability of the color of Hethemia pistasciaria which, in the males especially, readily fades or discolors through shades of yellowish green and ultimately yellow-brown.  From my own observations, it is unusually to see a truly pistaschio green or sage green specimen during or after periods of wet or extremely humid weather, suggesting that exposure to moisture may be a factor in the color change.  The gradations of color are many, and I have tried to illustrate the range of degrees of "fade" in the photographs above. 

The larvae of Hethemia pistasciaria are reported to feed on oak, birch, ironwood, basswood and blueberry (Ferguson, 1985).  According to Handfield (1999), this species has an adult flight season from early May nearly to the end of June for my general area.

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