MYCETOPHILIDvE. 15 



the bark of dead trees, etc. The larvae are said to moult sev- 

 eral times before pupating. The larvae of many species spin 

 delicate webs over the surface of 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. Per- 

 haps the most singular 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 sticking 

 together in dense patches, and will form processions some- 

 times 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 the 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 phosphorescent 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 indi- 

 vidual 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 bent around the eyes, 

 and their remaining portion applied to the breast between the 

 wings and the legs. The pupae of not a few are enclosed in a 

 cocoon of more or less density, spun by the larvae; others 

 enclose themselves in earthy cases. 



The study of the mature insect requires some care. Usually 

 a compound microscope is necessary for the detection of many 

 characters, especially of the more minute species, and gener- 

 ally, when there is doubt of the identity, it is best to mount 

 the whole insect or the more important parts under a cover 

 glass. 



In America, as elsewhere, but little study has been given to 



