Diapausing pupae of tasar silkworm, Antheraea mylitta Drury were injected with ox pancreas insulin (40 I.U. per ml) on day 150 to observe the effect of this vertebrate hormone on diapause physiology. Insulin at the dose of 5 μl (0.2 I.U.) per pupa exhibited its positive impact by enhancing the incidence of male and female moth eclosion, female moth weight, egg production (laid + unlaid), and fecundity and shortening of time taken for emergence in both sexes. But, 10 μl (0.4 I.U.) dose of insulin increased only the female eclosion and reduced the time taken for emergence in each sex when compared to that of control. Administration of higher dose of insulin (10 μ1 per pupa) decreased the egg production and fecundity. No significant changes were observed in hatchability and incubation phenomena of eggs laid by the treated females. Further, both the doses of insulin were able to bring about the morphometric changes of testis and ovary by altering their shape and size during pupal diapause. Thus, it reveals from the preliminary findings that vertebrate insulin induces diapause physiology of A. mylitta.