I could (and do) spend hours in one small stand of milkweed. Common Milkweed (Asclepia Syriaca) is a perennial native to Michigan and much of the eastern half of the US and Canada. It grows well in sandy, well-drained soil and spreads profusely by rhizomes.
Besides it's wonderful heady scent, Common Milkweed is a host to many kinds of insects. One of the more notable insects, other than the well known Monarch Butterfly, is the Milkweed Tussock Moth, which are classified in the subfamily Arctiinae.
Female Tussock Moths lay eggs in "rafts" and caterpillars are gregarious during instars 1-3, solitary in later instars, when marked with bright tufts. The ravenous caterpillars often defoliate patches of milkweed in a very short period of time.
The adult moths usually have unmarked gray wings, with bright yellowish-orange abdomens with black spots.
1: Common Milkweed (Asclepias syriaca)
2, 3 and 4: Milkweed Tussock Moth - Hodges#8238 (Euchaetes egle) Common. Hosts: Milkweed Notes: Two Broods (click images for lightbox view)