44 2 THE STUDY OF INSECTS. 



dack Mountains. The larvae live under the bark of decaying 

 branches, under fallen leaves, and in sap flowing from 

 wounded trees. 



Family MYCETOPHILID.E (My-cet-o-phil'i-dae). 



TJie Fungus-gnats. 



These flies are of medium or small size, and more or less 



mosquito-like in form. They are most 

 easily recognized by the great length 

 of the coxae (Fig. 518, c), and the 

 fact that all the tibiae are furnished 

 with spurs. They also differ from 

 the closely-allied families in lacking, 

 as a rule, whorls of hairs on the an- 

 tennae of the males (Fig. 519), and 

 in possessing ocelli. 



At first sight considerable varia- 

 . 518. FIG. 519. tion seems to ex i st j n the venation 



of the wings as shown in the three wings represented in 

 Figure 520 ; but in reality the variations are comparatively 

 slight. Vein I extends along the margin of the wing to the 

 end of vein 1 11^. Vein II varies in length. Vein III pre- 

 serves three branches in the more generalized form (Fig. 

 520,^); in some genera veins III, and III a+3 coalesce from 

 the apex of the wing backward for a greater or less distance 

 so that the base of vein III 2+3 appears like a cross vein (Fig. 

 520, b)', this coalescence may be complete, in which case vein 

 III is only two-branched (Fig. 520, c). Vein V is also 

 two-branched. It should be observed that the cross-vein 

 III-V extends more or less obliquely or even lengthwise of 

 the wing; while the base of vein III 4+6 may extend trans- 

 versely, and then is liable to be mistaken for a cross-vein 

 (Fig. 520, b, c). 



The flies are often found in great numbers on fungi and 

 in damp places where there is decaying vegetable matter. 

 They are active, and leap as well as fly. 



