Larvae of the cabbage looper,Trichoplusia ni(Hübner), parasitized byCopidosoma truncatellum(Dalman) consumed 35% more food and had a 30% higher maximum weight than unparasitized larvae. Food consumption and larval weight gain were exponential in both parasitized and unparasitized larvae, and parasitized larvae were more efficient in the conversion of ingested food into body weight. The greater consumption by parasitized larvae may affect plans for integrated biological control involvingC. truncatellum.