MYCETOPHILID^. 



swellings on the underside of the ventral segments, some- 

 times furnished with minute bristles or spines. 



The larvae present some of the most singular habits 

 among all diptera. They are gregarious, and live in or 

 upon decaying matter. Most of the species seem to pre- 

 fer fungus or fungoid substances, whence comes the com- 

 mon name of fungus-gnats applied to the mature insect. 

 The larvae of Sciara are found among decaying leaves, 

 in vegetable mold, in cow-dung, under the bark of dead 

 trees, etc.; they often live in the soil of potted plants. 

 The larvae are said to moult several times before pupat- 

 ing. The larvae of many species spin delicate webs over 

 the surface cf fungi, and on this web they live until ready 

 to pupate, when they spin a dense cocoon in sheltered 

 spots; others live within the decaying fungi. Perhaps 

 the strangest habits of all are those of species of Sciara, 

 which are even more gregarious than other members of 

 this family. They have the singular propensity of stick- 

 ing together in dense patches, and will form processions 

 sometimes twelve or fourteen feet in length, and two or 

 three inches broad. The phenomenon has been observed 

 frequently both in Europe and America, but the reason 

 therefor is not yet well understood, though the object of 

 migration seems to be the search for better feeding 

 grounds. Because of this habit, the name of 'army worm' 

 has been given to them. Yet more singular is the phos- 

 phorescent character of the larvae of some species. The 

 larvae, probably of Sciophila, were observed by Hudson 

 to be so luminous that 'the light of a single individual 

 kept in a caterpillar cage may be seen streaming out of 

 the ventilators at a distance of several feet.' 



The pupae of Mycetophilidae are free, that is they are 

 not contained within the larval skin, as is so commonly 

 the case with diptera. They are usually smooth, with 

 the legs applied to the breast and venter, the antennae 



