Larvae tend to be light brown or pinkish gray in color dorsally, with a brown to black head capsule and a yellowish brown thoracic plate. The body is marked with round dark spots on each body segment. The developmental threshold for larvae is about 11 degrees C. Larvae normally display six instars. Head capsule widths are about 0.30, 0.46, 0.68, 1.03, 1.66, and 2.19 mm in instars 1 through 6, respectively. Mean body lengths during the six instars are about 1.6, 2.6, 4.7, 12.5, 14.5, and 19.9 mm, respectively.
Young larvae tend to feed initially within the whorl, especially on the tassel.
When the tassel emerges from the whorl, larvae disperse downward where they burrow into the stalk and the ear. Mortality tends to be high during the first few days of life, but once larvae establish a feeding site within the plant survival rates improve. Larvae in the final instar overwinter within a tunnel in the stalk of corn, or in the stem of another suitable host. Duration of the instars varies with temperature. Under field conditions development time was estimated at 9.0, 7.8, 6.0, 8.8, 8.5, and 12.3 days for instars 1 through 6, respectively, for a mean total development period of about 50 days, but this varies considerable from year to year according to weather conditions.