The larva of Stethorus caseyi Gordon & Chapin is described. This species was collected at several sites on the Texas High Plains, where it was found feeding upon colonies of tetranychid spider mites on corn, Zea mays L. The mature (fouth instar) larva is described and illustrated. A diagnosis is provided, separating the larva of S. caseyi from that of the two other Stethorus species (Stethorus nigripes Kapur and Stethorus histrio Chazeau) collected in the same geographical and ecological area. A discussion of the geographic range of S. caseyi is presented, especially in comparison with the two other introduced species with which it is sympatric in West Texas.