Bark beetles oxidize the defensive monoterpenes of their host trees both to detoxify them and to convert them into components of their pheromone system. This oxidation is catalysed by cytochrome P450 (CYP) enzymes and occurs in different stages of the insect. We identified two new CYP4 genes in the Chinese white pine beetle (Dendroctonus armandi), and carried out bioinformatic analysis one the full-length nucleic acid sequences and deduced amino acid sequences. Differential expression of the CYP4 genes was observed between sexes, and within these significant differences amongst development stages, fed on phloem of Pinus armandi and exposed to stimuli((±)- α-pinene, (R)-(+)- α-pinene, (S)-(-)-α-pinene, (S)-(-)-β-pinene and (+)-3-carene) at 8 and 24 h, and their interactions were found upon exposure to host monoterpenes. Increased expression of CYP4 genes suggested that they play a role in the detoxification of monoterpenes released by the host trees. The differential transcript accumulation patterns of these bark beetle CYP4 genes provides insight into the ecological interactions of D. armandi with its host pine.,© 2014 The Royal Entomological Society.