120 NORTH AMERICAN DIPTERA 



Family Mycetophilidae — The Fungus Gnats 



I\Ioderately small, rather delicate, slender flies with elongated 



COXffi. 



Head small, rounded or somewhat elongate, usually closely applied 

 to the thorax. Eyes round, rather prominent; ocelli three, two or none, 

 the median one often small, the lateral ones frequently close to the 

 orbits; front broad in both sexes. Antennae elongated, composed of 

 twelve to seventeen segments, the two basal segments large or dif- 

 ferentiated, the others cylindrical, flattened or petiolated. Proboscis 

 usually short, rarely greatly lengthened; palpi rarely absent, composed 

 of three or four segments, usually inflexed. Thorax distinctly to 

 strongly arched, without transverse suture; scutellum small; metanotum 

 large. Abdomen composed of six or seven segments, cylindrical or com- 

 pressed either laterally or dorsoventrally, sometimes narrowed basally; 

 male genitalia projecting; ovipositor pointed, usually with two terminal 

 lamella?. Legs more or less elongated, the femora usually thickened; 

 coxge elongated; tibia with spurs and usually with series of short or 

 conspicuous bristles. Wings large; auxiliary vein present though some- 

 times very short; second longitudinal vein absent, or simulating a 

 crossvein; third vein arising from the first vein, usually at such an 

 angle as to simulate a crossvein, the crossvein sometimes appearing to 

 form the base of the third vein; fourth and fifth veins usually furcate, 

 sometimes simple; sixth vein sometimes rudimentary, never furcate; 

 the seventh usually short, often rudimentary or entirely absent; discal 

 cell absent, the second basal cell often open apically. 



The adults are found in moist places, especially about decaying 

 wood, on mossy rocks or moist humus, and prefer dark places. Many 

 of the species are quite small only a few being large and conspicuous. 

 They occur in a variety of habitats and some species are very restricted 

 in habitat although occurring over a very wide geographical range. 

 They may be collected throughout most of the year and when encoun- 

 tered often occur in large numbers. The larva live in moist soil, wood, 

 fungi, etc., and probably feed upon fungus growth. Pupation takes 

 place outside the larval skin, some species spinning cocoons. The habits 

 of the larva are particularly interesting and their investigation should 

 provide an entertaining and profitable field of study to some one inter- 

 ested in pure science for the fun of the thing. Johannsen* has mono- 

 graphed the family and only a small number of North American species 

 have been described since. 



Maine Agric. Exp. Sta. Bulls. 172, 180, 196. 200, 1909-12. 



