Abstract: 【Aim】 Sclerodermus spp. are important natural enemies of wood-boring pests in forests in China. The aim of this study is to clarify the taxonomic position of Sclerodermus within Aculeata by sequencing the mitochondrial genomes of four species of Sclerodermus and analyzing their mitochondrial genomic structure and phylogenetic position. 【Methods】 The mitochondrial genomes of four species of Sclerodermus (Sclerodermus alternatusi, Sclerodermus pupariae, Sclerodermus sichuanensis and Sclerodermus sp.) were sequenced using Illumina HiSeq. The mitochondrial genomes were then assembled and annotated to analyze their structural characteristics and base composition. In addition, the phylogenetic position of Bethylidae within Aculeata was analyzed by the phylogenetic tree constructed based on the sequences of 13 protein-coding genes (PCGs)of 46 fully annotated mitochondrial genomes of Hymenoptera species downloaded from NCBI and four mitochondrial genomes from this study by using Bayesian inference (BI) and maximum likelihood (ML) method. 【Results】 The full-length mitochondrial genomes of the four species of Sclerodermus range from 15 000 to 16 000 bp and comprise 37 genes, including 13 PCGs, 2 rRNA genes, 22 tRNA genes, and one non-coding control region. Among the 13 PCGs, the most frequently used amino acids are Ile, Leu, Phe and Met. Of the 22 tRNA genes, only trnS1 lacks the DHU arm, while the remaining 21 tRNA genes form the typical cloverleaf structure. Gene rearrangements were observed in 17 genes of the 37 genes, including 15 tRNA genes and 2 PCGs. The mitochondrial genomes of the four species of Sclerodermus exhibit gene shuffling in trnT-trnP, accompanied by gene inversion in trnT, as compared to those of the other Apocrita insects. The results of the phylogenetic analysis indicated that Bethylidae is monophyletic, with Sclerodermus being the most closely related to Cephalonomia.【Conclusion】 This study provided the mitochondrial genome characteristics of four species of Sclerodermus and demonstrated complex gene rearrangements. Phylogenetic analysis indicates that the Sclerodermus genus belongs to the Bethylidae family, supporting the traditional morphological classification result. The Bethylidae family is monophyletic and the sister to the Mutillidae family. These results lay the foundation for future classification and phylogenetic studies of the Bethylidae family.

Key words: Bethylidae; Sclerodermus, mitochondrial genome, gene rearrangement, phylogenetic relationship