Little barley is the only other important host in Georgia. Adult Hessian flies are small black flies about the size of a mosquito. Adults live about two days during which they mate. Females lay about 200 eggs in the grooves of the upper side of the wheat leaves. Young reddish larvae move along a leaf groove to the leaf sheath and then move between the leaf sheath and stem where they begin to feed on the stem above the leaf base.
Maggots become white after molting and appear greenish white when full grown.
The entire life cycle requires about 35 days at 70F. Newly hatched larvae are prone to drying while they are exposed on the leaf surface, but once larvae move to the stem base, they are protected from weather extremes. Maggots suck sap and stunt tillers presumably by injecting a toxin into the plant. Feeding by a single larva for several days is sufficient to completely stunt the growth of a vegetative tiller. Stunted vegetative tillers are dark green, do not elongate or produce new leaves and usually die after the maggots pupate. Infested jointed stems are short and the stem is weakened at the joint where feeding occurs.