为了揭示全变态类昆虫的系统发育关系,选择准新翅群3目3种昆虫作为外群,基于18S rDNA序列对全变态类11个目21科21种昆虫的系统发育关系进行研究。通过对18S rDNA序列进行多重序列比对,用似然比检验进行碱基替代模型的选择,分别利用ML法和贝叶斯法构建系统发育树。结果表明,全变态类昆虫聚为3个分支：双翅目+捻翅目、鞘翅目+(广翅目+(蛇蛉目+脉翅目))和膜翅目+(蚤目+长翅目)+(鳞翅目+毛翅目)。长翅类的单系性未得到支持。

In order to reveal the phylogenetic relationships of Holometabola, the fragments of 18S rDNA gene of 21 species in 21 families of 11 orders from Holometabola and 3 species in 3 orders from Paraneoptera as outgroups are used in the current analysis. After the alignment of the sequences, the likelihood ratio test is carried out to find the best model of nucleotide substitution fitting the data obtained from the alignment. The molecular phylogenetic trees are reconstructed with ML and Bayesian methods. The hierarchical likelihood ratio test is used to analyze the dataset. The result suggests a division into three large clades comprising Diptera+Strepsiptera, Coleoptera+(Megaloptera+(Raphidioptera+Neuroptera)) and Hymenoptera+(Siphonaptera+Mecoptera)+(Lepidoptera+Trichoptera) in the cladogram of Endopterygota. Mecopterida is not a monophyly.