Injured timothy heads, eaten by the wheat-head army-worm, have been more or less common in Iowa meadows for several years. This damage is usually noticed about haying time. In the summer of 1910 this insect became very abundant in the northern half of the state and caused a large amount of damage. The worst damage was reported from Pocahontas, Dickinson, Clay, Hancock, and Worth counties, but the area in which timothy was seriously injured extended as far south as Story county. However, the caterpillars, or larvae, as we will call them, were found in greater or less numbers all over the state. In some localities 50 to 90 per cent of the timothy heads in certain fields were injured.

Since the larvae feed mostly on timothy heads the damage is mainly to the seed crop, although occasionally the hay crop may be considerably affected. Great damage has been done in the past by this insect and it undoubtedly will cause damage in the future. In the hope of finding means of control for this pest and thereby reducing the injury, the study of the insect was taken up.