The eggs, deposited on leaves, are red and the newly hatched larva or maggot is also red for 4 or 5 days before turning white. As the larva matures, a translucent green stripe appears down the middle of its back. The maggot transforms into an adult fly inside a case called a puparium that is dark brown and resembles a flaxseed in size and shape. Hessian flies in North Carolina probably have three or more generations each year, except in the western Piedmont and Mountains, where they may have two. These additional generations are the result of warm weather in the fall.
Adult life is short, lasting an average of only two or three days.
Eggs hatch within a few days and the tiny maggots migrate to the base of the leaf sheath where they feed between the sheath and the stalk for 4 to 6 weeks. The pupae that survive the winter emerge as adults in the spring to begin the next generation. Damage to Small Grain Maggots feeding on wheat in the fall weaken and stunt plants. This may result in greater winter kill of plants and reduced spring tillering. Stems infested by the spring generation may die but usually lodge before harvest from feeding activity on the first or second node or joint.