Comparative study on size and growth of male and female larvae of Antheraea Mylitta drury in bivoltine generations

The body size and growth of male and female larvae of non-diapause-destined and diapause-destined generations of Tasar silkworm, Antheraea mylitta Drury were studied. It is inferred that male and female larvae of non-diapause-destined and diapause-destined generations showed marked differences in larval growth. There is a decrease in growth rate during the course of development of each larval instar and instar durations are inversely related to the weight at the time of initiation of a larval instar. A growth compensation mechanism operates during the development of the larval instars. The Dyar's rule factor was found to be higher in diapause-destined larvae of 1st and 2nd instar and in non-diapause-destined of 3rd and 5th instar.The regression estimates (R2) revealed that the larval growth was better in both generations with minor variation. About 90% total variation was explained by fresh body weight in enhancing larval growth rate in both sexes of 3rd instar. The linear trend for male and female was opposite in non-diapause-destined and diapause-destined larvae. The dry body weight of non-diapause-destined larvae had shown slow and better larval growth rate in 2nd instar in comparison to 1st instar which may be due to less consumption of food because insects are initially in infant stage. In 3rd instar low and non-significant compound growth rate was recorded for NDD male and female larvae, respectively. The slow growth in male and female diapause-destined larvae may be due to variation in abiotic factors. The non-diapause-destined larvae of 5th instar (feeding) had shown better linear trend. The higher negative growth rate was observed in diapause-destined male and female larvae during spinning which was due to physiological changes i.e. transformation of larva to pupa.