Ottawa (Dunrobin), ON Canada

20 August 2003   8:22PM EST  (top left)
30 June 2003   8:30PM EST  (top right)
9 August 2005   1:25AM EST  (second row left)
2 July 2003   8:38PM EST  (second row right)
16 June 2004   9:41PM EST  (third row left)
22 June 2003   9:06PM EST  (third row right)
26 June 2003   7:48PM EST  (bottom left)
22 June 2003   8:10PM EST  (bottom right)

My initial identification of Munroessa gyralis was based on Munroe, E., The Moths of North America North of Mexico, Fascicle 13.1, Pyraloidea Pyralidae (Part) (London: E.W. Classey, 1972-1974).  I have also relied on the Canadian National Collection in Ottawa and on Forbes, William T.M., The Lepidoptera of New York and Neighboring States, Primitive Forms, Microlepidoptera, Pyraloids, Bombyces (Ithaca, New York: Cornell University, 1923).  From Munroe's descriptions, it appears likely that most or all of the specimens illustrated above are the northern subspecies Munroessa gyralis serralinealis.

Munroessa gyralis exhibits strong sexual dimorphism, the male being somewhat smaller with a patterned forewing, whereas the larger female tends to show only vestigial traces of pattern on the forewing at best.

The forewing of the male Munroessa gyralis is generally buff-gray to gray-brown in color, marked in white and in dark gray-brown to blackish.  Near the base, an irregularly jagged line of dark gray-brown is typically bordered with white on both sides.  Half-way down the wing, at the inner margin, there is a white-edged loop enclosing a dark gray-brown area, sometimes with some white spots at the upper end.  Also beginning about half-way down the wing, at the costa, a dark brown line edged with white extends downward and then recurves to form an irregularly shaped loop enclosing two white areas separated by an area of the ground color.  A white line, usually edged with dark gray brown along the outer side, parallels the outer margin.  The hindwing is much paler, with patterning similar to that of the forewing.  Munroe (1972) indicates a forewing length of 8 to 12 mm for the male.

The female Munroessa gyralis generally has a much plainer forewing, ranging in color from orange-buff to dark gray-brown.  Traces of pattern similar to that of the male may be faintly present, but the wing in some specimens is virtually unmarked.  The pale hindwing may have some faint gray-brown banding, but sometimes appears quite plain.  Munroe (1972) indicates a forewing length of 11 to 14 mm for the female.

According to Munroe (1972), the larvae of Munroessa gyralis feed on waterlilies.

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