Spilosoma congrua

Antennae bipectinate in male and filiform in female.

Spilosoma spp. and Hyphantria cunea can be difficult to separate on sight. On Block Island, S. congrua is reliably distinguished from S. virginica and H. cunea most easily by its immaculate white abdomen and from S. latipennis by the orange scaling on its profemora. If the abdomen is not visible, S. congrua may be distinguished from H. cunea by its larger size; its forewings being less rounded near the apex; and its protarsi almost always being white dorsally and black medially, versus banded dorsally in the latter species. It may generally be distinguished from S. virginica based on the latter having some black banding on the dorsal surface of the protarsi. S. congrua varies greatly in the extent of black spotting on the forewings but with a different pattern than in H. cunea, which can have even more extensive black markings. S. virginica is never heavily marked, and those of S. latipennis are always immaculate.