Seasonal Abundance of the Screw-Worm in Northern Mexico1

Abstract
During 1953 regional similarities in activity patterns of the screw-worm, Cochliomyia hominivorax (Coquerel), were used to group infestations in northern Mexico into 5 provisional zones. In the first zone, widespread infestations were noted as early as April, with population peaks in July and October. In the second zone, sustained screw worm activity was limited to periods following rains. Patterns of screw-worm activity in the third zone were similar to those in the first, but the seasonal weather cycles were dissimilar. The fourth and fifth zones showed a single peak of screw-worm activity in the late summer.