MYCETOPHILHXE. 45 



In the typical subfamily the principal genus, Mycetophila, with 

 some others, possesses a laterally compressed abdomen, which, 

 with the hump-shaped thorax and low small head, gives them the 

 appearance of fleas, the resemblance being further heightened by 

 the power of leaping to some extent by means of the well- 

 developed hind legs. 



There are no macrochastse in the family, the majority of the 

 species being almost devoid of all but a microscopic pubescence 

 and a few bristly hairs on certain parts of the body. The tibiae, 

 however, are in most cases (except SOIARII^) furnished with two 

 or three rows of bristles, which afford good characters for classi- 

 fication, and alsa with apical spurs. The coxae are more or less 

 enlarged, often very considerably so, in all the subfamilies except 

 SCIAHIKJE, in which they are nearly normal. 



The imagos are found in shady places in fields and woods, the 

 larval stages being passed in fungi in a large number of the 

 species, in rotten wood in many others, whilst a limited number 

 are aquatic. A few species live in vegetable mould, under the 

 bark of trees or in cow dung, and many occur in marshy places. 



About four hundred extinct species are known, a good 

 number of these belonging to the more extensive recent genera, 

 though they appear geologically as early as the Mesozoic period, 

 in the Purbeck beds. 



Popularly they are known as fungus-gnats, from their breeding 

 in fungi, and it has been claimed that their presence is of economic 

 value to the farmer by keeping down the fungi which would 

 otherwise by their numbers injure trees and shrubs. 



Some species are said to hibernate and reappear in early 

 spring when, according to Heeger, they " copulate after a few 

 days, generally in the evening. After six or ten days, the female, 

 if the weather is moist and rainy, lays its eggs on the fungi growing 

 on old horse-chesnuts, singly, twenty or thirty on the same fungus. 

 The larva? hatch after eight or ten days." 



The family characters of the adult Mycetophilid may be briefly 

 summarised as follows : 



Head small, rounded or moderately elongate ; eyes rounded or 

 sometimes reniform, separated in both sexes by a broad frons. 

 Ocelli two or three ; when only two, they are placed each 

 touching an eye-margin ; when three, they may be in the form of 

 a more or less flattened triangle, or practically in a straight line, 

 but the middle one is always on the centre line of the frons. 

 Antenna? elongate, of 12 to 16 joints ; the scapal or two basal 

 joints differentiated, the rest generally cylindrical, in some genera 

 compressed, more rarely pectinate. Proboscis short, blunt ; quite 

 elongate in one or two genera only (Onoriste is the only Oriental 

 genus). Palpi of three or four joints, incurved, the 1st very small, 

 occasionally one joint much more strongly developed than the 

 others. 



