【Aim】 This study aims to identify the salivary gland proteins of the obligate parasitic natural enemy Procecidochares utilis for the invasive plant Eupatorium adenophorum and mine potential gall-inducing effectors. 【Method】 Label-free quantitative proteomics was employed to identify and quantitatively analyze the salivary gland proteins of the first- and second-instar larvae of P. utilis. Spatiotemporal expression profiling of the transcriptome was employed to identify the genes with specifically high expression in gall-inducing critical instars and salivary glands. 【Result】 A total of 3 485 proteins were identified in the salivary glands of the first- and second-instar larvae of P. utilis, with 3 368 proteins successfully quantified. Among them, 3 234 proteins were common to both instars, and 137 differentially expressed proteins were identified. Ultimately, one gene (evm.model.CTG2.720) exhibiting specifically high expression in the salivary glands and during the gall-inducing critical instar was identified. Bioinformatics analysis revealed that protein encoded by this gene belonged to the apolipoprotein D (ApoD) family and exhibited secretory protein characteristics. 【Conclusion】 This study identified an ApoD family member in the salivary gland proteome of P. utilis larvae through systematic protein profiling, hypothesizing its potential role as a gall-inducing effector. These findings establish a theoretical foundation for unraveling the molecular mechanisms underlying gall formation induced by P. utilis and advancing eco-friendly biocontrol againstE. adenophorum.