The genera Euchaetes Harrison and Cycnia Hübner (Arctiidae: Arctiinae: Callimorphini) have been extensively studied by chemical ecologists and behaviorists. Males of Cycnia tenera Hübner produce courtship pheromones and species' specific ultrasound signals, whereas Euchaetes uses only ultrasound. Some have suggested that the behavior found in Euchaetes evolved more recently. Euchaetes, Cycnia, and Pygarctia Grote are commonly misplaced among genera. This study addressed the species limits of Euchaetes, Cycnia, and Pygarctia and tested the reciprocal monophyly of the genera. Forty-four adults representing 22 of 35 species were dissected. Eighty-nine characters (207 states) were defined. Data were analyzed using maximum parsimony implemented with Paup* (1000 random reps). Taxon jackknifing and decay analyses were performed to assess clade support. Our results suggest that although species are commonly misplaced among these genera they can be distinguished on the basis of genitalic characters. Our tree supports the interpretation that the ultrasound use in Euchaetes is more recently evolved.