Larva in achenes...Neolasioptera helianthi (Felt)
Infested achenes appear normal or slightly swollen. Larvae pupate inside and emerge through a hole in the crown....Heavily infested flower heads produce leaves in the center. Hosts: Helianthus spp. Distr.: widespread in North America.
”- Raymond J. Gagne: (1989) The plant-feeding gall midges of North America©