Caterpillars of the genus Hylesia (Lepidoptera: Saturniidae: Hemileucinae) can cause agricultural damages and dermatological lesions by direct contact to its urticating bristles. The biological control can regulate populations of these insects, but their natural enemies are poorly known. The occurrence of Harpactor angulosus (Lepeletier and Serville, 1825) (Reduviidae: Harpactorinae) predating caterpillars of Hylesia spp. is described. Adults of this predator were captured in an area of secondary forest in Viçosa, Minas Gerais State, Brazil and their pairs individualized in the field to obtain eggs. Adults of this predator presented sex dimorphism, with smaller males than females. They were found predating caterpillars of Hylesia spp., isolated from others to avoid the aposematic defense of this prey, when grouped. The presence of this predator, in the field, demonstrates its potential for the biological control of defoliating caterpillars. Studies on biological aspects and alimentary habits are important to understand the importance of H. angulosus in the biological control of defoliating caterpillars.