Bot flies (Oestridae) are obligate endoparasites of mammals, and their extraordinary diversification is of great importance in understanding the evolution of parasitism. However, evolutionary analysis of Oestridae has long been impeded by lack of information. Here, the first three mitochondrial genomes of nasal bot flies (Cephalopina titillator, Cephenemyia trompe and Rhinoestrus usbekistanicus) and a comparative mitochondrial genomic analysis between subfamilies of Oestridae are presented. Contrasting to many other parasites, mitochondrial genomes of oestrids are conserved in structure and genes retain the same order and direction as the ancestral insect mitochondrial genome. Nucleotide composition is highly heterogenous, with Gasterophilinae possessing highest GC content and smallest genomic size. Mitochondrial evolutionary rates vary considerably, with Hypodermatinae and Oestrinae exhibiting a faster average rate than Cuterebrinae and Gasterophilinae. In addition, the first phylogenomic analysis covering all four bot fly subfamilies was conducted, supporting monophyly of Oestridae and a sister-group relationship of Hypodermatinae and Oestrinae. The only topological ambiguity is Cuterebrinae being a sister-group of either (Hypodermatinae + Oestridae) or Gasterophilinae. Thus, we suggest that mitochondrial genomes carry a great potential for phylogenetic analysis of Oestridae, and more information of Cuterebrinae is needed to illuminate the early evolutionary radiation and parasite-host coevolution of bot flies.

蝇蝇（Oestridae）是哺乳动物的专性内寄生物，它们的非凡多样化对理解寄生虫的进化具有重要意义。但是，由于缺乏信息，对兽科的进化分析长期以来一直受到阻碍。在这里，鼻蝇蛆前三线粒体基因组蝇（Cephalopina titillator，Cephenemyia风筒和Rhinoestrus usbekistanicus），并进行了大麦科亚科之间的线粒体基因组比较分析。与许多其他寄生虫相反，雌性线粒体的线粒体基因组在结构上是保守的，基因保持与祖传昆虫线粒体基因组相同的顺序和方向。核苷酸组成是高度异质的，胃蝇科具有最高的GC含量和最小的基因组大小。线粒体的进化速率差异很大，其中Hypodermatinae和Oestrinae的平均速率比Cuterebrinae和Gasterophilinae快。此外，进行了涵盖所有四个蝇蝇亚科的首次系统进化分析，以支持大麦科的单系性和次要皮科和小皮科的姐妹群关系。唯一的拓扑歧义是Cuterebrinae是（Hypodermatinae + Oestridae）或Gasterophilinae的姐妹组。因此，我们建议线粒体基因组具有很大的潜力进行大肠科的系统发育分析，并且还需要更多有关线虫的信息以阐明蝇的早期进化辐射和寄生虫-宿主协同进化。