Labellar Modifications of Muscomorpha Flies (Diptera)

Labella of 35 families of flies were examined, primarily by scanning electron microscopy techniques. The labellar lobes were capable of everting beyond Stage IV (Graham-Smith 1930a) only in Phoridae and Calypterata. The ability to evert the lobes beyond Stage IV to the Stage VI position was positively correlated with presence of prestomal teeth. Much variation in prestomal tooth numbers and structure was seen, and the rasps of Glossina were determined to be prestomal teeth. Pseudotracheal ring tips were highly modified and variable. Pseudotracheal diameter was measured and considered to be an important reflection of diet in nature. Families were characterized using the above adaptations, but these labial structures had many convergences and parallelisms and, therefore, were often unreliable taxonomic characters. Diet was correlated, wherever possible, with structural variations; most fly diets, however, remain unknown, so postulations were presented using morphological evidence.