Heavily-damaged heads are gnarled and cupped inwardly, producing few seeds. Eggs are laid individually or in groups in depressions between the bracts of the sunflower bud. The newly-emerged larvae move to the bases of developing seeds or bracts. They use their rasping mouthparts to feed on the plant tissues in these locations.
Mature larvae drop from the head and burrow into the soil.
If conditions are favourable, they pupate and emerge the same season. Otherwise, they remain in the soil and overwinter as larvae in cocoons or, in some cases, as pupae. Usually, the larvae pupate in the spring. The adults start to emerge in late- June. The adult midges only live for 2-3 days and are difficult to find in the field.