ABSTRACT
The range caterpillar infests an estimated 7.7 million ha of rangeland in the United States in what appears to be two distinct populations, separated by 260 or more kilometers. The range caterpillar overwinters in the egg stage. Eggs are laid from late September through late November. Hatching is triggered by late spring and summer rainfall, generally from May until early July depending on the area and season. Range caterpillars normally lay their full complement of eggs in a single, cylindrical mass of up to 150 eggs. Range caterpillar population densities appear to be lower on severely overgrazed rangeland. Evaluation of insecticides for range caterpillar control was initiated in the early 1960s. Toxaphene was rapidly adopted because of cost and reliability. The Range Caterpillar integrated pest management (IPM) program was the first rangeland IPM program developed in the nation.
