Transcriptome Characterization and Identification of Chemosensory Genes in the Egg Parasitoid Anastatus orientalis, Along with Molecular Cloning, Sequence Analysis, and Prokaryotic Expression of the Odorant Binding Protein 8 (AoOBP8) from A. oriental

<i>Anastatus orientalis</i>, a prominent egg parasitoid of <i>Lycorma delicatula</i>, demonstrates considerable potential for biological control. <i>A. orientalis</i> is dependent on host volatiles to identify and locate appropriate hosts for reproduction, with its olfactory system playing a vital role in volatile detection. There is little known about the chemosensory genes in <i>A. orientalis</i>. Therefore, here, we conducted a transcriptome analysis of the males and females from <i>A. orientalis</i>. Overall, 24 odorant binding proteins (OBPs), 4 chemosensory proteins (CSPs), 26 odorant receptors (ORs), 3 gustatory receptors (GRs), 3 ionotropic receptors (IRs), and 2 sensory neuron membrane proteins (SNMPs) were identified by transcriptome analysis. The values for fragments per kilobase per million (FPKM) indicated that the chemosensory protein gene families in <i>A. orientalis</i> exhibit different expression levels in male and female adults, with some genes showing significant differences and displaying sex-biased expression. Furthermore, RACE technology, phylogenetic analysis, and expression analysis were used to investigate the role that <i>AoOBP8</i> plays in olfaction in <i>A. orientalis</i>. <i>AoOBP8</i> was highly expressed in females and the heads of adults, indicating that the gene has a crucial role to play in the search for hosts and in oviposition in female adults, while the head is crucial in recognizing chemical information. These results contribute to a deeper understanding of the functions of chemosensory protein gene families in <i>A. orientalis</i> and offer a reference for developing biocontrol methods for forestry pests.