At 5,000 feet altitude, in the vicinity of Laggan, Nemeophila petrosaflies during July. This is one of our commoner moths, and appears to be the only bombycid of common occurrence in the district. Although occasionally round near timber 1ine, it is rare at that elevation. Under natural conditions only one flight occurs in the season, and larvæ from eggs of that flight hibernate principally at an early stage. In the house, with a warmer night temperature, larvæ resultant from the July flight will go to imago late in October instead of hibernating. Inthe wild environment, a second flight is prevented by the low night temperature. Petrosa frequents moist banks, ditches, margins of old roads, and open ground well supplied with plants. A great majority of the individuals seen in flight are males, the disparity in relative number of males and females observed resulting from the quieter disposition of the females. The males are very restless and readily take flight, thereby attracting observation.