The Symphyta has long been recognized as a paraphyletic grade forming the base of the remaining Hymenopteran, and the superfamily relationships within Symphyta remain controversial. Here, the first two representative mitochondrial genomes from the superfamily Siricoidea and Xiphydrioidea (Hymenoptera: Symphyta) are obtained using next-generation sequencing. The complete mitochondrial genome of Xiphydria sp. is 16,482 bp long with an A + T content of 84.18% while the incomplete one of Tremex columba is 16,847 bp long and A + T content is 81.69%. All 37 typical mitochondrial genes are possessed in both species. The secondary structure of tRNAs and rRNAs for both species are successfully predicted. Compared with the ancestral organization, seven and five tRNA genes are rearranged in mitochondrial genomes of Tremex and Xiphydria, respectively, which are the most rearrangement events within Symphyta. The rearrangement patterns in Tremex and Xiphydria present in this study are all novel to the Symphyta. Phylogenetic relationships among the major lineages of Symphyta are reconstructed using mitochondrial genomes. Both maximum likelihood and Bayesian inference analyses highly support Symphyta is a paraphyletic grade, Xyeloidea + (Tenthredinoidea + (Pamphilioidea + (Xiphydrioidea + (Cephoidea + (Orussoidea + Apocrita))))).

长期以来，共生植物被认为是形成其余膜翅目的基础的近亲属，而共生植物内的超家族关系仍然存在争议。在这里，使用下一代测序获得了超家族天狼蛛和剑藻（膜翅目：Symphyta）的前两个代表性线粒体基因组。Xiphydria sp。的完整线粒体基因组。长度为16482 bp，A + T含量为84.18％，而Tremex columba的残基之一长度为16847 bp，A + T含量为81.69％。这两个物种都拥有全部37种典型的线粒体基因。成功地预测了两种物种的tRNA和rRNA的二级结构。与祖先组织相比，Tremex和Xiphydria的线粒体基因组分别重排了7个和5个tRNA基因，这是Symphyta中最重排的事件。Tremex和Xiphydria中的重排模式目前这项研究对Symphyta都是新颖的。利用线粒体基因组重建了共生植物主要谱系之间的亲缘关系。最大似然和贝叶斯推断分析都高度支持Symphyta是共生的等级，Xyeloidea +（Tenthredinoidea +（Pamphilioidea +（Xiphydrioidea +（Cephoidea +（Orussoidea + Apocrita）））））。