Poison Hemlock Moths, and their sole host plant, Poison Hemlock (Conium maculatum), were introduced from Europe. The plant arrived in North America in the 1800s, and the first recorded moth in New York State in 1973. The moth was also accidentally introduced to the US northwest shortly after, and has since spread rapidly from both locations. Adults overwinter and will start laying eggs on plants in early spring. Larvae emerge in early May, and fatten up through July, rolling leaves and feeding on foliage, flowers, and buds. In late summer, the caterpillars pupate and emerge as adults.
Jane Mangold, with MSU Extension, provides a nice summary of the Poison Hemlock in the Ravalli Republic article “Weed of the Week: Poison hemlock needs to be handled with care.”
Size: Wingspan 17-19 mm
Photo by: Kristi DuBois on 3/27/22 in Missoula, MT