Abstract:［Objective］The purpose of this study is to examine the relation between the sex ratio of Ericerus pela and its symbiotic bacterial Arsenophonus． ［Methods］ The symbiotic bacterial diversity in male Ericerus pela was determined through sequencing 16S rDNA gene library． PCR amplification for Arsenophonus was performed by using two 16S rDNA specific primers and 23S rDNA specific primer． The molecular detection of Arsenophonus in six geographic populations of E． pela，namely Zhaotong，Kunming，Jinkouhe，Hangzhou，Changchun，and Jianghua，were performed by semiquantitative PCR． The absolute concentrations of Arsenophonus in E． pela of Zhaotong，Kunming，Jinkouhe geographic populations were determined using absolute quantitative real-time PCR． ［Results］ Two different 16S rDNA sequences were obtained; the sizes were 445bp and 1462bp respectively． A 23S rDNA sequence was obtained，the size was 582bp．Some E． pela individuals of Hangzhou and Jianghua were not infected with Arsenophonus． The contents of Arsenophonus in E． pela of Zhaotong were significantly higher than that of Kunming and Jinkouhe，while the contents of Arsenophonus from the latter two geographic populations were not significantly different． ［Conclusion］Arsenophonus is not responsible for the sex ratio of E．pela．