I was out taking a walk Sunday afternoon and saw many different small moths flying out from hiding in the grass and blueberry bushes. Most were too small and fast to get a good look at them. The one shown above flew and ducked under some grass blades just long enough for me to get a few snapshots before it took off. Later I went out again and saw dozens of them in a forest clearing full of bracken fern. The species is Northern Petrophora (Petrophora subaequaria, Family Geometridae) and its larvae feed only on ferns with bracken fern (Pteridium aquilinum) apparently the principle host plant. Photos at Bug Guide show the larvae on fronds of Osmunda fern.
Some brief information on Northern Petrophora (Petrophora subaequaria)
Superfamily Geometroidea (Geometrid and Swallowtail Moths)
Family Geometridae (Geometrid Moths)
Genus/species Petrophora subaequaria
Wing span to 19 mm, speckled tan forewings with yellowish veins, antemedial and postmedial lines white edged and parallel. There is a small black dot in the center of the wings.
As with many moths not directly injurious to crops and forestry there is little information on the life history of Northern Petrophora. With so many adult moths appearing now in my bracken field it seems that mating and egg laying occur in the spring.
Northern Petrophora occurs in North America from New Brunswick to Alberta, along the Great Lakes east to New England, and then south sporadically along the Appalachians to North Carolina.
Beadle, D. and Leckie, S. (2012). Peterson Field Guide to Moths of Northeastern North America. Houghton Mifflin Harcourt Publishing Company, Boston. 640 pages.
Voss, Edward G. (1991) “Moths of the Douglas Lake Region (Emmet and Cheboygan Counties), Michigan: IV. Geometridae (Lepidoptera),” The Great Lakes Entomologist: Vol. 24 : No. 3 , Article 11. Available at: http://scholar.valpo.edu/tgle/vol24/iss3/11