Ottawa (Dunrobin), ON Canada

8 July 2003   10:32PM EST  (left)
11 July 2004   1:04AM EST  (right)

My initial identification of Ostrinia nubilalis was based on Covell (1984), and subsequently checked against Munroe, E., in Dominick, R.B. et al., The Moths of America North of Mexico, Fascicle 13.2A, Pyraloidea Pyralidae (Part) (London: E.W. Classey, 1976).  I have also relied on Forbes, William T.M., The Lepidoptera of New York and Neighboring States, Primitive Forms, Microlepidoptera, Pyraloids, Bombyces (Ithaca, New York: Cornell University, 1923).

Ostrinia nubilalis is sexually dimorphic, both male and female having similar patterns of lines on the forewing, but the yellow ground color of the wing heavily suffused with dark purplish brown in the male.  Covell (1984) indicates a wingspan of 2.4 to 3.2 cm, the female being larger than the male.

The forewing of the male Ostrinia nubilalis is yellow in the basal area, with slight gray-brown shading, and no translucent quality to its appearance.  The antemedial line runs in broad zigzags, edged with yellow in the inner side.  The postmedial line runs in a series of shallow, narrow zigzags, curving slightly inward just below the costa, then bulging outward before turning sharply inward again about 2/3 of the way down the wing, after which it makes a near-right-angle bend and extends to the inner margin.  The median is heavily shaded with purplish brown except at the inner margin.  The dark discal spot is easily distinguished against a somewhat rectangular patch of yellow.  Outside the postmedial line there is a jagged band of yellow, followed by a heavy subterminal "scribble" of dark purplish gray-brown.  The hindwing is mostly a lighter shade of purplish gray-brown, with a yellow blotch near the outer margin.

The female Ostrinia nubilalis has yellow wings with a hint of grayish shading in the median, against which the rectangular yellow blotch is clearly visible.  The antemedial and postmedial lines are similar in shape to those of the male.  The subterminal line is sharply dentate.  The hindwing is paler yellow with faint lines.

Munroe (1976) refers to the larva of Ostrinia nubilalis, known as the European Corn Borer, as "one of the major agricultural pests of North America."  The caterpillars bore in corn stalks and ears of corn, and also feed on a wide variety of other plants.

My records to date for Ostrinia nubilalis (each date representing "the night of", and excluding those for which I am not confident of the identification) are in the table below: