A comparative study on the mouth parts of medically and veterinarily important flies, with special reference to the development and origin of the prestomal teeth in cyclorrhaphous Diptera

Abstract

A comparative study on the mouth parts of medically and veterinarily important flies was performed, and the development and origin of the prestomal teeth in cyclorrhaphous flies were discussed. The types of the mouth parts of Musca-species were divided into three groups, viz. domestica, conducens and crassirostris-groups based on the development of the prestomal sclerites. Observations using both a scanning electron microscope (SEM) and a light microscope made clear the external characters and the quality of the prestomal teeth, and showed the true affinities of mouth parts. Intermediate forms were found among the three groups, and gradual development of the prestomal teeth and discal sclerite were observed. It was supposed that the prestomal sclerites of Musca-species gradually evolved from the undeveloped type to the developed, sclerotized type that have the acute labella and the pseudotracheae of a reduced number, acquiring the food-habit which is omnivorous to haematophagous. In Calypteratae, the species which have developed prestomal teeth were confined to those which are predacious or haematophagous. Basically, the muscid, calliphorid and sarcophagid flies have prestomal teeth regardless of their food habits. But in tachinids and some species of anthomyiids, the prestomal teeth were vestigial or absent. Moreover, in most of the species belonging to Aschiza and Acalypteratae, the prestomal teeth were absent, although they were found in some phorid species. Considering the phylogeny and the present state of prestomal teeth in cyclorrhaphous flies, the origin of the developed prestomal teeth found in the higher calypterate flies of medical and veterinary importance can presumably be traced back to the ancestral Anthomyiidae.