108 Mr. F. W. Edwards on the 



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

 M(/. (Diptera Nematocera). ^y h^. W. Edwards, B.A., 

 F.E.S. 



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



For many years the small oimts of tlie genus Mycetobia 

 lijive been a great puzzle to all Dipterists wlio have attempted 

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

 tact that the adults appear to diverge very slightly in structure 

 from tyjiical members of the Mycetophilid^, while, on the 

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

 family lUiYPHiD^ *, which has always been regarded as 

 widely se|)arated from the M YCETOPHILID^. 



O.-ten-Sacken, the foremost Dipterist of the last century, 

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

 "... I have shown the perfect unity of type prevailing among 

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

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

 tobia puUipes, which is not peripneustic, like the larvjB of the 

 other Mycetophilid^, but amphipneustic; it shows the most 

 remarkable resemblance to the larva of Rhyphus, and often 

 occurs together with it. Three trustwortiiy observers have 

 described the larvai as ann)hipneustic : Lyonet, Dufour, and 

 Ferris. The two latter have found the larva together with 

 that of L'hyphus, and were struck by their resemblance, 

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

 relationship between the larvai of Mycetobia 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. Araer., 

 March 1915, 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 ^lons. D. Keilin, whose studies (as yet unpubhshed) 

 have not only confirmed the observations of the early 

 authors f, but have shown that the resemblance between the 

 larvae of Mycetobia and likyphus is even greater than they 

 supposed. 



* Throughout this paper the terra Rhyphm has been used, though 

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

 Anisopus, 



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

 Agricultural Experiment fetation, Bulletin 177 'j. 



