Abstract: The effects of parasitism by the koinobiontic parasitoid Meteorus pulchricornis (Wesmael) on food consumption, weight gain, and food utilization in the penultimate instar larva of Spodoptera exigua Hübner were studied by the gravimetric method in the laboratory. The results indicated that the parasitism resulted in a significant reduction of the amount of food consumed, the growth rate, and food utilization of the host larva. The parasitized larva consumed less food, which were 29.89% and 48369% of that of the unparasitized on the 4th and 5th day, respectively. In line with the food consumption, the weight gain of the parasitized larva was less than the unparasitized, which were 21.51%, 38.87% and 14.42% of that of the unparasitized on Day 3, 4 and 5 after parasitization, respectively. The relative growth rate of the parasitized larva was significantly lower than the healthy larva from Day 3 to Day 5 after parasitization. The food utilization of the parasitized larva measured with the efficiency of conversion of ingested food (ECI) and the efficiency of conversion of digested food (ECD) for body mass was significantly less than the unparasitized larva, but the approximate digestibility (AD) was increased as expected, while the unexpected phenomenon is that the above pattern was reversed on the 4th day after parasitization. The unexpected changes in nutrition indices on the 4th day after parasitization may be attributed to the effect of much less amount of food consumed by the parasitized larva while gaining more weight at the same time. The study indicates that parasitism of M. pulchricornis obviously inhibits food consumption, food utilization, and growth of its host S. exigua larvae

Key words: Meteorus pulchricornis, Spodoptera exigua, parasitism, food consumption, growth, food utilization