Impact of arthropod predators on mortality of early instars of the range caterpillar,Hemileuca oliviaeCockerell, was assessed in three field experiments. In the first two experiments, first instars ofH. oliviaewere introduced into experimental units; predators were excluded from half of the units insecticidally and with cages. Results showed no effect on larval survivorship from the initial level of larvae, indicating density-independent mortality, and a significant effect resulting from exclusion of potential predators. Evidence from sweep-net samples, pitfall traps, and general observations suggested an important role for generalist predators, especially the antCrematogaster punctulataEmery. Possible impact of spiders, cicindelids, mantids, and gryllacridids is considered. In the third experiment,C. punctulatawas shown to be a predator ofH. oliviae. Implications for importance of arthropod predators in saving rangeland forage are discussed.