Cotesia ruficrus (Hymenoptera: Braconidae) is an endoparasitic natural enemy of various Lepidopteran pests, and it plays a significant role in integrated pest management. In the field survey of maize fields, we found for the first time that the indigenous parasitoid C. ruficrus parasitized the major invasive pest Spodoptera frugiperda (Lepidoptera: Noctuidae) in China. We identified 18 odorant-binding proteins (CrufOBPs) of C. ruficrus through the RNA-Seq method, and PCR analysis showed that 13 out of the CrufOBPs were highly expressed in antennae. Two CrufOBPs, CrufOBP3 with the highest antennal expression and CrufOBP17 with antenna-specific expression, were selected for protein biosynthesis in the prokaryotic protein expression system and subjected to protein purification. Through fluorescence binding assay, seven maize volatile compounds were selected for the antennal electroantennography (EAG) study, and the results indicated that female C. ruficrus exhibited distinct responses to these volatiles at different concentrations. Octanal and 2-heptanone of 10 mg mL⁻¹ were chosen for olfactory behavioral experiments because of their high EAG responses, and the results showed that C. ruficrus adults were significantly attracted at certain concentrations. Furthermore, in the cage experiments, 10 mg mL⁻¹ of 2-heptanone significantly increased the parasitism rate of C. ruficrus on S. frugiperda. These findings not only provide a theoretical basis for studying the odorant-binding protein family of C. ruficrus but also contribute to the development of novel pest control strategies for this invasive pest management.

Cotesia ruficrus（膜翅目：茧蜂科）是多种鳞翅目害虫的内寄生天敌，在害虫综合防治中发挥着重要作用。在玉米田田间调查中，我们首次发现本土寄生蜂C. ruficrus寄生于我国主要入侵害虫草地贪夜蛾（鳞翅目：夜蛾科）。我们通过RNA-Seq方法鉴定了C. ruficrus的18个气味结合蛋白（CrufOBP），PCR分析显示其中13个CrufOBP在触角中高表达。选择两种CrufOBP，触角表达最高的CrufOBP3和触角特异性表达的CrufOBP17，在原核蛋白表达系统中进行蛋白生物合成，并进行蛋白纯化。通过荧光结合分析，选择了七种玉米挥发性化合物进行天线触角电图（EAG）研究，结果表明雌性C. ruficrus在不同浓度下对这些挥发性化合物表现出不同的反应。由于EAG反应较高，因此选择10 mg·mL ^-1的辛醛和2-庚酮进行嗅觉行为实验，结果表明，在一定浓度下， C. ruficrus成虫被显着吸引。此外，在笼养实验中，10mg·mL ^{-1的2-庚酮显着增加了}红果蝇对草地贪夜蛾的寄生率。这些发现不仅为研究C. ruficrus气味结合蛋白家族提供了理论基础，而且有助于开发这种入侵性害虫管理的新型害虫控制策略。