Telenomussp., and to a lesser extent,Trichogrammasp., were important in the regression phase of a gradation ofSymmerista canicostaFranclemont, the so-called redhumped oakworm. Two years following the outbreak,Telenomusparasitized more than 80% of the eggs near ground level. When parasite populations were moderate,Telenomustended to be most abundant near ground level whereasTrichogrammatended to be most abundant in the upper parts of the forest. When populations ofTelenomuswere dense, parasitization was high at all levels in the forest. Both parasites successfully parasitizedS. canicostaeggs in the laboratory.