Ottawa (Dunrobin), ON Canada

26 May 2005   10:30PM EST  (top left)
9 May 2005   11:15PM EST  (top right)
3 June 2005   9:31PM EST  (center)
4 June 2005   12:15AM EST  (bottom left)
7 June 2004   1-:54PM EST  (bottom right)

Identification of Marathyssa basalis is made somewhat challenging by this moth's habit of resting with its wings furled, although it is more likely to show at least part of its wings unfurled than its relative Marathyssa inficita (Hodges 8955).  Nevertheless, those of us photographing unposed live specimens are often frustrated by this moth's reluctance to open out its wings.

Marathyssa basalis, also known as the Light Marathyssa, has a yellowish forewing, shaded to varying degrees with gray-brown and reddish brown.  The basal area is bordered by an antemedial band of dark brown edged in white on the inside and in black on the outside.  The median is crossed by a diffuse line of gray-brown to reddish-brown.  The reniform spot is evident as a white crescent with a black spot in the upper end.  The double black postmedial line is filled with white and most evident at the inner margin.  Along the costa, there is a narrow streak of whitish gray crossed by dark lines, followed by a fairly clear broader streak of yellow, which has some reddish shading from the postmedial line and fading back to yellow outward.  The hindwing is mainly yellowish gray, shaded darker gray and reddish near the anal angle, with a white postmedial line.  Covell (1984) indicates a wingspan from 2.5 to 3.2 cm.

According to Handfield (1999), the larva of Marathyssa basalis feeds on poison ivy, making it one of my favorite insects given Ottawa's reputation as the poison ivy capital of Canada!  For my general area, he indicates an adult flight season from about the last week of April to the beginning of July.

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