none Laboratory studies were made of the growth, food consumption and food utilization by parasitized and unparasitized Sylepta derogata (F.) larvae. Growth was lower in parasitized than in unparasitized larvae. Parasitized larvae consumed significantly less food than unparasitized larvae. The dry weight-fresh weight consumption index did not differ significantly between the 2 types of larva. Parasitism increased the efficiency of digestion but had no effect on the efficiencies of conversion of ingested and digested food to body matter.