Introduction In recent years, many problems have appeared in silkworm (Bombyx mori), rearing as a result of pesticide applications to cultivations, especially when mulberry trees are grow next to cultivated plants. Study of insecticides on silkworms includes their toxicity and effects on retardation of development and growth, fecundity, mortality, food utilisation and economic parameters (Bizhannia, 2005). Admiral®, as an insect growth regulator (IGRs), is a juvenile hormone analogue, with relatively low mammalian toxicity that was first registered in Japan for control of public health pest (Miayamoto et al., 1993). Lately, this insecticide has been used for the control of different pests and much research has been completed on the efficacy of this IGR. Silkworm larvae are extremely susceptible to a number of different IGRs, that at very low doses induces in 5th instar larvae a “Non-Spinning Syndrome” and developmental arrest (Kim et al., 2002; Etebari, 2000). The persistence of insecticides used to control insect pests of mulberry and air drift of pesticides from other neighbouring crops are reported and include study of biochemical changes of silkworm due to insecticide residue (Kim et al., 2002). Also it have been studied its effects on biological traits of silkworm in different stages. The aim of the present study was to study the effect of Admiral® residue on biological parameters of silkworm larvae.