Data on the life histories of dipterous insects belonging to the fauna of the zone of emergent hydrophytes in lakes of northern Michigan are recorded. The following species are included: 1. Asteromyia phragmites Felt (Cecidomyiidae) inhabits the internodal pith cavities of Phragmites communis Trinius. Larva and pupa are described. Three hymenopterous parasites were reared. 2. Hormomyia sp. (Cecidomyiidae) produces tuberous swellings on the culm bases of Carex vesicaria L. Larva and pupa are characterized. One parasite was reared. 3. Oligochaetus sp. (Dolichopodidae) mines and bores in spike rush and bulrushes. Larva and pupa are described. 4. Cordylura latifrons Loew (Scatophagidae) bores in the culm bases of bulrushes. Larva and puparium are described. A braconid parasite was reared from the puparium. 5. Chloropisca sp. (undescribed; Chloropidae). 6. Diplotoxa microcera Loew (Chloropidae). 7. Leucopis griseola Fallen (Ochthiphilidae). 8. Agromyza longipennis Loew (Agromyzidae) mines subepidermally in bulrushes.