Phylogenetic relationships among holometabolous orders and mtDNA gene order distribution. The phylogenetic relationships among holometabolous orders are based on the work of Wiegmann et al. . Black name, order for which there is no available full-length mtDNA; dark-green name, order exhibiting the insect ancestral gene order; variously colored name, order that has a gene order different from the insect ancestral gene order. **, ***, several distinct gene orders differing from the insect ancestral gene order. In the case of Diptera, only the family Culicidae has a gene order different from the ancestral arrangement. In the case of Coleoptera the gene order change is restricted to Mordella atrata . Genes coded on the α strand (clockwise orientation) are light/deep-green. Genes coded on the β strand (counterclockwise orientation) are red or orange. Alternation of colors was applied for clarity. Gene names are the standard abbreviations used in this paper; tRNA genes are indicated by the single-letter IUPAC-IUB abbreviation for their corresponding amino acid in the figure. On the branch leading to the relative holometabolous order, the genomic change characterizing the gene order is shown. In case of multiple gene orders within a single order, the changes were not depicted to avoid overcrowding.