Systematic Position of the Genus Mycetobia^ Mg. 109 



At M. Keilin's suggestion, I liave devoted some study to 

 tlie adult structure of the Mycetophilid^ and Rhyphid.e, 

 in order to ascertain wlietlier any ciiaracters can be found to 

 support conclusions based on the study of larvse and pupa3. 

 Without claiming to have made at all an exhaustive in- 

 vestigation, I think I may safely state not only that such 

 characters do exist, but that they should be taken into account 

 in the classification of the Diptera as a whole. 



In order to explain clearly what these characters are, it 

 will be necessary to give a brief comparative account of the 

 structure of the mouth-parts and the venation in the two 

 families in question. In referring to the mouth-parts of the 

 Mycetophilid^ I am relying partly on my own observations, 

 but chiefly on the excellent work lately published by Dr. R. 

 Frey (Acta Soc. Fauna et Flora Fennica, xxxvii. no. 2, lOlo). 



Mouth-parts. 



MandiUes. — There seems to be no trace of these in either 

 of the two families. 



Fi.v. 1. 



Labrum, epipliarynx, and hypopharynx of (a) Olhiogasfer africanus, Edw., 

 {b) Rhyphus fenestralis, Scop., and (c) Mycetobia pallijjes, Mg. 



Labrum. — In both the Mycetophilid^ and Rhyphid^ 

 the labrum is very much reduced, being, as a rule, almost 

 entirely membranous. There is, nevertheless, a considerable 

 amount of variation. In the Rhyphid genus Olbiogaster a 

 distinct chitinized piece is present on the upper side, the lower 

 side (the so-called epipharynx) being chiefly membranous ; 

 in Rhyphus the upper side is membranous, the lower side 

 more or less chitinized and provided with a fringe of hairs 

 towards the tip; in Mycetobia the whole labrum is mem- 

 branous. 



