The larvae of Nymphomyiidae (Diptera, Insecta) - ancestral and highly derived?

Larval head structures of Nymphomyia dolichopeza were examined and described in detail. The conditions are compared to those of other dipteran representatives. Our results support the monophyly of Nymphomyiidae. Potential apomorphies are dimorphic crochets on the abdominal prolegs and the complete loss of the tentorium. Possible synapomorphies of Nymphomyiidae and Deuterophlebiidae could be the rows of spatulate macrosetae covering the ventral surface of the labrum-epipharynx, the presence of distinct teeth along the anterior premento-hypopharyngeal margin, the absence of labral microtrichia and some other affinities concerning the life history of the two groups. A clade Blephariceromorpha is also supported by some larval features. Potential synapomorphies of Nymphomyiidae, Deuterophlebiidae and Blephariceridae are the vestigial M. labroepipharyngalis, the absence of a movable premandible, crochet-tipped prolegs, the complete loss of spiracles and non-retractable anal papillae. A clade Nymphomyiidae and Chironomidae is only weakly supported by characters of the larval head. The anteriorly serrate and posteriorly fused hypostoma is a potential apomorphic character. Our results support neither phylogenetic affinities between Nymphomyiidae and Axymyiidae nor a sistergroup relationship between Nymphomyiidae and the remaining Diptera. However, a comprehensive cladistic analysis is not presented in our study.