Numbers
Worldwide about 6000 spp. in 544 genera
209 species in North America
Identification
You have to look closely at some members of this family to distinguish the six legs common to all insects. The adult butterfly's front pair of legs is modified into two small "brushes", and only four legs are used for walking around.
Print References
(1) Opler/Malikul, Peterson Field Guide to Eastern Butterflies