321 



and forcing them to get to the surface in much the same manner as 

 earthworms. Whether we have a numher of species in America that 

 are addicted to this hahit, or only one, remains to be discovered. Most 

 of the species of the family feed upon decaying vegetable matter. 



MYCETOPHILID^ 

 Myce;tobia divergens Walker 



Mijcctobia divergent Walker, Ins. Saund., Diptera, Pt. 1, 1856, p. 418. 

 Mycetophila persica Biley, Prairie Farmer, June 15, 1867, Vol. 35 (n. s., 5), 



No. 19, p. 397. 

 Mycetobia sordida Packard, Guide to Study of Insects, 1869, p. 388. 

 Myceiobia marginalis Adams, Kans. Univ. Sci. Bull., Vol. 2, No. 2, 1903, p. 21. 



Larva (PI. LXXX, Fig. 12). — Length, 9-1 1 mm. White, semi- 

 transparent. Head brownish, eye-spots black, surrounded by paler 

 color. Thoracic segments with brown markings of variable extent 

 and depth, pattern on dorsum generally as in figure ; laterally the pale 

 markings are generally in the form of an irregular vertical stripe on 

 middle of segments and a pale posterior margin, those on prothoracic 

 segment being usually connected on upper portions, whereas on the 

 other two segments they are separated throughout their length ; the 

 pale markings of the lateral areas are continued over the ventral sur- 

 face for a short distance, and there are also two wedge-shaped pale 

 marks extending from the posterior margin of each segment which are 

 usually short on the prothoracic segment and much longer and broader 

 on the other two segments. Abdomen without brown marks. 



Head about 1.5 as long as broad, tapering slightly anteriorly; 

 labrum protruding, its ventral surface densely covered with fine down- 

 wardly directed hairs; mandibles as in Figure 11; labial plate as in 

 Figure 13; maxillse stout, of moderate length, with short papillae; sur- 

 face of head wnth a few short hairs. Prothoracic respiratory organs 

 (Figs. 5 and 6) slightly raised above level of segment, their margins 

 rugose; trachea connected by a stout transverse trunk at division of 

 first and second thoracic segments ; immediately behind the spiracular 

 opening is a strong branch which is subdivided near its base, one of 

 the divisions being directed forward, entering the head, the other 

 directed backward; abdomen without' spiracles, the lateral tracheal 

 branches bifurcate, without the normal terminal connection with the 

 outer wall of abdomen ; apices of the two main parallel tracheal trunks 

 slightly projecting beyond surface of last segment in life, retracted in 

 dead specimens, their apical margins with a number of weak radiating 

 hairs. 



