Hylyphantes graminicola is a resident spider species found in maize and cotton fields and is an important biological control agent of various pests.Previous studies have demonstrated that stress from elevated CO2 and Wolbachia infection can strongly affect spider species.Thus,based on CO2 levels (400 ppm,current atmospheric CO2 concentration and 800 ppm,high CO2 concentration) and Wolbachia status (Wolbachia-infected,W+ and Wolbachia-uninfected,W-),we divided H.graminicola individuals into four treatment groups: W-400 ppm,W-800 ppm,W+ 400 ppm,and W+ 800 ppm.To investigate the effects of elevated CO2 levels (W-400 vs W-800),Wolbachia infection (W-400 vs W+ 400),and the interactions between these two factors (W-400 vs W+ 800),high-throughput transcriptome sequencing was employed to characterize the de novo transcriptome of the spiders and identify stress-related differentially expressed genes (DEGs).De novo assembly of complementary DNA sequences generated 86 688 unigenes,23 938 of which were annotated in public databases.A total of 84,21,and 157 DEGs were found among W-400 vs W-800,W-400 vs W+ 400,and W-400 vs W+ 800,respectively.Functional enrichment analysis revealed that metabolic processes,signaling,and catalytic activity were significantly affected by elevated CO2 levels and Wolbachia infection.Our findings suggest that the impact of elevated CO2 levels and Wolbachia infection on the H.graminicola transcriptome was,to a large extent,on genes involved in metabolic processes.This study is the first description of transcriptome changes in response to elevated CO2 levels and Wolbachia infection in spiders.