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Insulin signaling can regulate various physiological functions, such as energy metabolism and reproduction and so on, in many insects, including mosquito and locust. However, the molecular mechanism of this physiological process remains elusive. The tobacco cutworm, <i>Spodoptera litura</i>, is one of the most important pests of agricultural crops around the world. In this study, phosphoinositide 3-kinase (<i>SlPI3K</i>), protein kinase B (<i>SlAKT</i>), target of rapamycin (<i>SlTOR</i>), ribosomal protein S6 kinase (<i>SlS6K</i>) and transcription factor cAMP-response element binding protein (<i>SlCREB</i>) genes, except transcription factor forkhead box class O (<i>SlFoxO</i>), can be activated by bovine insulin injection. Then, we studied the influence of the insulin receptor gene (<i>SlInR</i>) on the reproduction of <i>S. litura</i> using RNA interference technology. qRT-PCR analysis revealed that <i>SlInR</i> was most abundant in the head. The <i>SlPI3K</i>, <i>SlAKT</i>, <i>SlTOR</i>, <i>SlS6K</i> and <i>SlCREB</i> genes were decreased, except <i>SlFoxO,</i> after the <i>SlInR</i> gene knockdown. Further studies revealed that the expression of vitellogenin mRNA and protein, Methoprene-tolerant gene (<i>SlMet</i>), could be down-regulated by the injection of dsRNA of <i>SlInR</i> significantly. Furthermore, a depletion in the insulin receptor by RNAi significantly decreased the content of juvenile hormone III (JH-III), total proteins and triacylgycerol. These changes indicated that a lack of <i>SlInR</i> could impair ovarian development and decrease fecundity in <i>S. litura</i>. Our studies contribute to a comprehensive insight into reproduction, regulated by insulin and the juvenile hormone signaling pathway through nutrition, and a provide theoretical basis for the reproduction process in pest insects.