Variability of the key features and revision of a group of closely related species of grassflies (Diptera, Chloropidae, Meromyza)

The following external morphological features of members of the genus Meromyza Mg. have been analyzed: the ratio of the height of frontal triangle to the length of the head; the presence of black setae on the lower surface of genae; the degree of manifestation of ocellus spot; the ratio of the length of mesonotum to scutellum; the length and color of the mid strip of the mesonotum and its degree of manifestation on the scutellum; and the thickness of hind femurs. Additionally, the size and shape of anterior and posterior processes of the postgonite, and the type of attachment of the posterior process have been investigated. The authors have determined the range of variability of key features applicable to the reliable identification of closely related species of grass flies in the “meigeni” species group of the genus Meromyza, as well as the usefulness of CO1 mtDNA sequences for this purpose. The authors propose to re-instate the name M. laeta Meigen, 1838 (instead of using the name M. meigeni Nartshuk, 2006), to include seven species into the cluster “meigeni”, and to substitute the name of the cluster “meigeni” with the name “variegata”.