We've had three more moth caterpillar species in the yard in the last week. The first one is the Milkweed Tussock Moth Caterpillar (Euchaetes egle) another milkweed specialist. We most often find this caterpillar on common Milkweed (Asclepias syriaca) but this summer I saw several young instars on our Butterfly Milkweed.
Moths and Caterpillars of the North Woods, the female caterpillars gather pyrrollizidine alkaloids from decaying plants for the purpose of defence and pheromone production.
All three of these caterpillars overwinter in a pupal form, having one generation per year. It's nice to know that they will have plenty of places in our yard under the leaf litter or fallen logs to survive our cold Minnesota winters.