THE MYCETOPHILlD.gi OF NORTH AMERICA. 211 



inner side ; maxillse with inner and outer lobes, the former 

 usually serrate ; and a small chitinized labium. The body of 

 the larva is without hair or bristles except that in some genera 

 there are two transverse rows of simple or bifid ambulacral 

 setulas on the margin of each abdominal segment on the ventral 

 side. There are usually eight pairs of spiracles, which in some 

 of the genera at least, are protected by small chitinized conical 

 projections, the anterior pair being largest. 



The pupae are extricated, that is, not encased in the con- 

 tracted skin of the larva. The legs are applied to the breast 

 and venter, the antennae are bent around the eyes, and extend 

 between the wings and legs. The prothoracic spiracle is placed 

 a little above the root of the wing and immediately behind the 

 antenna. The abdominal spiracles are distinct on both sides 

 of the abdomen. The pupa is smooth, white in color and 

 frequently encased in a delicate cocoon. The pupae of those 

 forms whose larvae live in mushrooms are usually found in the 

 soil and among the decaying parts of the plant. The larval 

 and usually the pupal life also is of short duration, though the 

 insect may hibernate as a pupa. The time which elapses from 

 the egg to the adult stage may not exceed two weeks in mid- 

 summer. 



The imago may be distinguished from other flies by the 

 following characters : Antennae usually i6 jointed, occasion- 

 ally 12 to 17 jointed; palpi usually 3 or 4 jointed; ocelli present 

 except in one or two genera. Thorax highly arched, scutellum 

 small, setose. Abdomen with 6 to 9 visible segments, cylin- 

 drical, conical or oval and laterally compressed ; the male with 

 complex hypopygium, the female with a short ovipositor with 

 2 terminal lamellae. In the male the seventh and eighth seg- 

 ments are usually very small. The coxae are very strong and 

 excepting in the Sciarinco and a few of the lower genera, are 

 much elongated ; the femora are more or less thickened, later- 

 ally compressed, often setose ; the tibiae usually slender, spurred, 

 and setose; tarsal claws with teeth. The wings are usually 

 oval, hairy or microscopically setulose, and without the cell 

 ist M2 (discal cell). The wing venation is quite varied though 

 it may readily be reduced to four types. The first and most 

 primitive is that of Palceoplatyura (fig. 70) ; in the second, 

 CeroplatincE, Macrocerince, Ditomyia (fig. 71) the basal section 



