Background: Culex tritaeniorhynchus and Culex pipiens pallens are the major vectors of the Japanese encephalitis virus and Wuchereria bancrofti, the causative agent of filariasis. The knowledge of mitochondrial genomes has been widely useful for the studies on molecular evolution, phylogenetics and population genetics.

Background Despite the medical importance of the genus Culex , the mitochondrial genome (mt genome) characteristics of Culex spp. are not well understood. The phylogeny of the genus and particularly the generic status of the genus Lutzia and the subgenus Culiciomyia remain unclear. Methods The present study sequenced and analyzed the complete mt genomes of Lutzia halifaxia , Lutzia fuscanus and Cx. ( Culiciomyia ) pallidothorax and assessed the general characteristics and phylogenetics of all known 16 mt genome sequences for species in the genera Culex and Lutzia. Results The complete mt genomes of Lt. halifaxia , Lt. fuscanus and Cx. pallidothorax are 15,744, 15,803 and 15,578 bp long, respectively, including 13 PCGs, 22 tRNAs, two tRNAs and a control region (CR). Length variations in the Culex and Lutzia mt genomes involved mainly the CR, and gene arrangements are the same as in other mosquitoes. We identified four types of repeat units in the CR sequences, and the poly-T stretch exists in all of these mt genomes. The repeat units of CR are conserved to different extent and provide information on their evolution. Phylogenetic analyses demonstrated that the Coronator and Sitiens groups are each monophyletic, whereas the monophyletic status of the Pipiens Group was not supported; Cx. pallidothorax is more closely related to the Sitiens and Pipiens groups; and both phylogenetics analysis and repeat unit features in CR show that Lutzia is a characteristic monophyletic entity, which should be an independent genus. Conclusions To our knowledge, this is the first comprehensive review of the mt genome sequences and taxonomic discussion based on the mt genomes of Culex spp. and Lutzia spp. The research provides general information on the mt genome of these two genera, and the phylogenetic and taxonomic status of Lutzia and Culiciomyia . Electronic supplementary material The online version of this article (10.1186/s13071-019-3625-2) contains supplementary material, which is available to authorized users.

Despite worldwide distribution and rich diversity, the knowledge of mitochondrial genome (mtgenome) characteristics within the family Tenebrionidae (Coleoptera) is still very limited, and phylogenetics remain unresolved for the family. In this study, the mtgenomes for 12 species are newly sequenced and annotated. Three of the species represent the first report of complete mtgenomes from the subfamily Alleculinae. Comparative analysis of 36 tenebrionid mtgenomes finds that gene composition and order are the same as a theoretical ancestral insect mtgenome, and AT bias, length variation, and codon usage are consistent with other reported beetle mtgenomes. Some intergenic overlap and gap sequences may contain phylogenetically informative information, whereas neither the conserved nor repeat sequences in the control region do. The subfamilies Lagriinae, Pimeliinae, Stenochiinae, and Alleculinae are found to be monophyletic, and the subfamilies Diaperinae and Tenebrioninae polyphyletic in our study. Furthermore, Lagriinae is sister to the rest of the subfamilies. At the tribal level, the tribes Lagriini in the subfamily Lagrrinae; Strongyliini in Stenochiinae; Cteniopodini in Alleculinae; and Triboliini, Opatrini, and Amarygmini in Tenebrioninae are monophyletic; while Diaperini in Diaperinae, and Tenebrionini in Tenebrioninae are polyphyletic.

Delia antiqua is a major underground agricultural pest widely distributed in Asia, Europe and North America. In this study, we sequenced and annotated the complete mitochondrial genome of this species, which is the first report of complete mitochondrial genome in the family Anthomyiidae. This genome is a double-stranded circular molecule with a length of 16,141 bp and an A+T content of 78.5%. It contains 37 genes (13 protein-coding genes, 22 tRNAs and 2 rRNAs) and a non-coding A+T rich region or control region. The mitochondrial genome of Delia antiqua presents a clear bias in nucleotide composition with a positive AT-skew and a negative GC-skew. All of the 13 protein-coding genes use ATN as an initiation codon except for the COI gene that starts with ATCA. Most protein-coding genes have complete termination codons but COII and ND5 that have the incomplete termination codon T. This bias is reflected in both codon usage and amino acid composition. The protein-coding genes in the D. antiqua mitochondrial genome prefer to use the codon UUA (Leu). All of the tRNAs have the typical clover-leaf structure, except for tRNA Ser(AGN) that does not contain the dihydrouridine (DHU) arm like in many other insects. There are 7 mismatches with U-U in the tRNAs. The location and structure of the two rRNAs are conservative and stable when compared with other insects. The control region between 12S rRNA and tRNA Ile has the highest A+T content of 93.7% in the D. antiqua mitochondrial genome. The control region includes three kinds of special regions, two highly conserved poly-T stretches, a (TA)n stretch and several G(A)nT structures considered important elements related to replication and transcription. The nucleotide sequences of 13 protein-coding genes are used to construct the phylogenetics of 26 representative Dipteran species. Both maximum likelihood and Bayesian inference analyses suggest a closer relationship of D. antiqua in Anthomyiidae with Calliphoridae, Calliphoridae is a paraphyly, and both Oestroidea and Muscoidea are polyphyletic.

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