108 Mr. F. W. Edwards on the 



ly. — On the Systematic Position of the Genus Mycetobia, 

 Mq. {Diptera Nematocera). Bj F. W. EDWARDS, B.A., 

 F.E.S. 



(Published by peruiissiou of the Trustees of the British Museum.) 



For many years the small gnats of the genus Mycetohia 

 have been a great puzzle to all Dipterists who have attempted 

 to arrive at a natural classification of the order, owing to tlie 

 fact that the adults appear to diverge very slightly in structure 

 from typical members of the Mycetophihd^, while, on the 

 other hand, the larvae differ little, if at all, from those of the 

 family Rhyphid^ *, which has always been regarded as 

 widely separated from the j\l YCETOPHILID^. 



0;ten-Sacken, the foremost Dipterist of the last century, 

 thus states the problem (Berl. ent. Zeit. vol. xxxvii. p. 442) : 

 *'...! have shown the perfect unity of type prevailing among 

 the larvai of the different genera of this family. There is one 

 exception to this rule, however. ... It is the larva of Myce- 

 tobia paUipes, which is not peripneustic, like the larvai of the 

 other MycetophiliDuE, but amphipneustic; it shows the most 

 remarkable resemblance to the larva of Hhyphus, and often 

 occurs together with it. Three trustworthy observers have 

 described the larvae as amphipneustic : Lyonet, Dufour, and 

 Ferris. The two latter have found the larva together with 

 that of I\hyj)hiiSy and were struck by their resemblance, 

 although fully aware of the differences. ... If there is a real 

 relationship between the larvse of Mycetohia and lihyphus, 

 we have a right to expect a corresponding relationship 

 among the imagos. But, as this relationship does not exist, 

 this is a problem yet to solve." 



In spite of the high standing of the observers quoted by 

 Osten-Sacken, a recent writer (Knab, Ann. Ent. Soc. Amer., 

 March iyi5, p. 95) has got over the difficulty by suggesting 

 *' that the supposed difference rests upon an error of observa- 

 tion." That this is not the case, however, has recently been 

 found by Mons. D. Keilin, whose studies (as yet unpublished) 

 have not only confirmed the observations of the early 

 authors j, but have shown that the resemblance between the 

 larvae of Mycetobia and Rhyphus is even greater than they 

 supposed. 



* Tbrougbout this paper the term Rhyphus has been used, though 

 strictly, according to the rules of priority, it should be replaced by 

 Aiiisopus. 



t The main facts were also confirmed by Johannsen in 1910 (' Maine 

 Agriciiltiual Experiment Station, Bulletin 177'). 



