The wingspan of this species is two to three and one-fourth inches. The male and female have different coloration. For males, the upperside of the wings is yellow with brown spots, and a faint line can be seen in the middle of the forewing. The line parallels the edge of the forewing. The upperside of the female’s wings is raspberry colored with markings similar to those of the male. The hindwing of both sexes contains a large black spot with a blue and white center surrounded by a yellow band, then a black line followed by another yellow band. The underside of the male’s wings is yellow, while the underside of the female’s wings is red-brown. The large spot is visible on the hindwing of both sexes.
The io moth is found statewide. The adults are active starting in late May and can be found in wooded areas and savannas. The adult does not feed, while the larvae feed on many species of plants. One generation is produced in northern Illinois while two generations are produced annually in the southern part of the state.