Larva of fifth instar silkworm, Bombyx mori L. (Lepidoptera: Bombycidae), parasitized by uji-fly, Exorista sorbillans (Weidemann) (Diptera: Tachinidae), consumed less food and egested less faecal matter than unparasitized one in the instar period. Uji-fly infested worm showed increased digestibility in the last 2 days while the unparasitized larva ingested excessive amounts of food than needed during these days. A reduction of 18.1% in the mean weight of parasitized worm at pupation was recorded. Further, parasitization resulted in 50.7% reduction in the mean cocoon weight and 51.12% reduction in the mean shell weight. Parasitized worms started spinning a day earlier than the healthy ones and the cocoon spun by the former was abnormal.