Ottawa (Dunrobin), ON Canada

28 April 2007   10:07PM EDT  (top)
18 April 2007   8:48Pm EDT  (center left)
20 April 2007   9:16PM EDT  (center right)
16 April 2005   10:17PM EDT  (bottom left)  (female)
16 April 2005   10:16PM EDT  (bottom right)  (female)
The bottom two photos are of the same specimen.

Phigalia titea, sometimes called the Half-Wing, is one of two species of Phigalia recorded from the Ottawa area (J. D. Lafontaine, pers. comm., 2001). My initial identifications were based on Covell (1984) and Handfield (1999).  Some information on the species has also been obtained from McGuffin, W.C., "Guide to the Geometridae of Canada (Lepidoptera), II.  Subfamily Ennominae.  2", Memoirs of the Entomological Society of Canada, no. 101 (Ottawa: 1977).

The forewing of the male Phigalia titea is light whitish gray.  Antemedial, medial and postmedial lines are dark gray, often with thickening where they cross the most prominent veins.  The lines are spaced out on the wing, with the medial line slightly closer to the pm line than to the am line.  The antemedial line is often preceded by a brownish gray shade in the lower half of the wing near the inner margin.  The postmedial line is frequently followed by a brownish gray shade for most of its length, generally most evident in the lower part of the wing.  The hindwing is slightly paler, with similar but fainter lines.  Not infrequently, melanic specimens are encountered (see photo at center right) in which the entire wing is usually dark gray to blackish, with dark gray to black tracing on the veins.  McGuffin (1977) notes a wing expanse of 30 to 40 mm.

The female Phigalia titea has very small, stubby vestigial wings and is flightless.  The specimen illustrated in the bottom two photos was collected immediately behind my house at the base of a sheet set up with a mercury vapor lamp by visiting collector J. Delisle, and was brought to my door to be photographed live within minutes of being captured.

Although the male Phigalia titea has some similarities to the male Phigalia strigataria, the two can usually be distinguished on the basis of P. strigataria being slightly smaller and darker gray, with medial and postmedial lines nearly touching or touching at the inner margin.  Also, live specimens of P. strigataria usually exhibit less hindwing when in a resting position than P. titea.

According to Handfield (1999), the larva of Phigalia titea has been reported to feed mainly on basswood, elm, birch, maple and oak, but also on various other trees and shrubs. For my general area, he indicates the adult moth flies from about the end of March into mid-June, but at my location I have recorded Phigalia titea later than mid-May on only one occasion.  McGuffin (1977) notes an adult flight season of late March to late May.

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