Relationships between morphological and genetic trees of 4 marine orthoclad and related genera, Clunio, Semiocladius, Telmatogeton and Thalassosmittia, of the dipteran family Chironomidae as well as a terrestrial genus Smittia and a freshwater genus Cricotopus were examined. In the genetic tree, there were 3 lineages; Smittia, Semiocladius and other 4 genera, comprising Cricotopus. Telmatogeton and Thalassosmittia formed an intimate clade in spite of their different affiliations to the subfamily. Semiocladius and Clunio made a small clade in the morphological tree, whereas Telmatogeton and Thlassosmittia did not form a clade by themselves. Cricotopus participated in the largest cluster. These results suggest that Clunio, Telmatogeton and Thalassosmittia have derived from a freshwater ancestor and there be some morphological parallelisms.