Northern Prairie Wildlife Research Center serves both Moths of North America and Butterflies of North America . The first step in using these two resources to identify a specimen is to decide whether you are dealing with a moth or a butterfly. Although some, such as the Io moth are brightly colored or have colorful eyespots, most moths are drab, with cryptic wing patterns.
Bodies tend to be bulky and are often quite pubescent.
If you can get a good look at them, the shape of the antennae is the best way to distinguish butterflies from moths. Except for one group of tropical butterflies, all butterflies have simple antennae that end in a swelling or club. The clubs may be very pronounced, as in the Nokomis Fritillary or more subtle, as in the White-dotted Cattleheart . Unfortunately, there are no simple characteristics that universally distinguish moth caterpillars or pupae from those of butterflies. Two resources that may help if you are trying to identify a caterpillar are Caterpillars of Eastern Forests and Caterpillars of Pacific Northwest Forests and Woodlands .