Larve &e. of Mycetobia, Ditomyia, and Symmerus, 33 
1V.—On the Structure of the Larve and the Systematic 
Position of the Genera Mycetobia, Mg., Ditomyia, Winn., 
and Symmerus, Walk. (Diptera Nematocera). By D. 
Kern, D.Sc. (from the Quick Laboratory, University 
of Cambridge). 
[Plates IT.-V.} 
I. Mycetobia pallipes, Meigen. 
The larve of Mycetobia pallipes were first described and 
fi.ured by Lyonnet (1832) and Guérin-Mén: ville (1835). 
Dufour (1841) and notably Perris (1870), after a more 
complete study of these larvae, showed that their respiratory 
system is amphipneustic and called attention to their external 
resemblance to the larvee of Rhyphus fenestralis, Scop. 
Osten-Sacken (1892), referring to the papers of these 
entomologists, again raised the question of the larval resem- 
blance of Mycetobia and Rhyphus, which in the adult stage 
seemed to be so different. But since Osten-Sacken the 
majority of entomologists dealing with Mycetobia un- 
questioningly referred this genus to the family Myceto- 
philidze, passing over in silence the peculiar structure of its 
larvee. hose who gave the matter any attention either 
doubted the correctness of the original observations of Dufour 
aud Perris, or did not admit the value of larval characters 
in determining the systematic position of Insects. 
However, a study of the life-history and larval morphology 
of Mycetobia pallipes, Mg., and Rhyphus fenestrahs, whicly | 
carried out in 1912-13 on material collected at Chaville 
(near Paris) has led me to the conclusion that the resem- 
blance between these larvee aud their difference from those 
_of Mycetophilidz is much deeper than was ever supposed. 
In the present paper I will point out only the main 
characters common to the early stages of Mycetobia pallipes 
and Rhyphus fenestrais, but not found in those of 
Mycetoplilide. 
A more detailed study of the larval anatomy of Mycetobia 
I propose to reserve for a special paper dealing with the 
family Rhyphide. 
Characters common to Mycetobia Characters common to all .the 
pallipes (Pl. Il. fig. 2, Pl. V. Mycetophilidee (Pl. 111.) except 
figs. 86, 37, 38) and Rhyphus the genera Ditomyia and Sym- 
fenestralis (Pl. I. fig. 1). MerUus. 
1. The eggs are invested with a 1. Eges are more or less scattered 
gelatinous mass which is fixed on the surface of the fungus 
to a solid substratum. or rotten wood. 
2. Eggs are pear-shaped. 2. Eggs are elongated or sub- 
spherical. 
Ann. & Mag. N. Hist. Ser. 9. Vol. iii. 3 
