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Allatostatin C (PISCF/AST) is a neuropeptide gene that affects juvenile hormone (JH) synthesis in the corpora allata. Juvenile hormone acid O-methyltransferase (JHAMT) is a key gene in the JH biosynthetic pathway. In this study, two genes encoding DaAST and DaJHAMT were cloned. Both DaAST and DaJHAMT were expressed in the larvae, pupae and adults of Chinese white pine beetle (Dendroctonus armandi), and highly expressed in the head and the gut. The expression of the two genes was induced by JH analog (JHA) methoprene and the functions of the two genes were then investigated by RNAi. Considering the role of hormones in metamorphosis, JHA significantly induced DaAST and DaJHAMT in the larval stage. DaAST knockdown in larvae, pupae and adults significantly increased the DaJHAMT mRNA levels. Moreover, knockdown of DaAST instead of DaJHAMT increased pupae mortality and the abnormal rate of emergence morphology and reduced emergence rates. However, knockdown of DaJHAMT instead of DaAST significantly reduced frontalin biosynthesis in adult males. The results showed that DaAST acts as an allatostatin and inhibits JH biosynthesis, and that JHAMT is a key regulatory enzyme for JH synthesis in the D. armandi. [ABSTRACT FROM AUTHOR]