259 



XXXVIII, Fi^^ 6). In other respects the larvae closely resemble 

 those of Leia, the locomotor organs when present being inconspicuous 

 and the abdominal spiracles black and easily distinguished. 



Pupa (PI. XXXVIII, Figs. 5, 7). — General appearance similar to 

 that of pupae of Mycetophilinae, but differing noticeably in having 

 the thorax much less swollen and not declivitous anteriorly, the an- 

 tennae much longer, frequently extending to apices of wings, and the 

 fore, mid, and hind legs of conspicuously different lengths, and no- 

 ticeably shorter than in Mycetophilidae. The abdomen is sometimes 

 furnished with short setulose hairs and has 6 pairs of exposed spir- 

 acles as have Lcia and allied genera, the basal (seventh) pair very small 

 and discoverable only by careful examination and partial dissection 

 of base of abdomen. The legs in many species are very much shorter 

 than in Sciara prolifica, which is the species figured, the hind pair 

 sometimes reaching only to apex of fourth segment. The abdomen 

 also lacks the short setulae that are present in prolifico. 



HABITS OF LARVAE 



The larvae are essentially scavengers, feeding upon decaying vege- 

 table matter, and manure, but some species do considerable damage 

 to cultivated mushrooms, and under natural conditions feed on fungi. 

 Occasionally in early spring some species appear in immense numbers 

 in plant-propagating houses, having been introduced in leaf-mold in 

 very late fall or in winter while in the egg or larval stage. 



Some species, usually when full-grown, have a peculiar habit of 

 leaving the place where they have fed and traveling on the surface of 

 the ground in a rope-like aggregation, which may attain a diameter 

 varving from an inch to three inches and a length of eighteen inches 

 to five feet and contain several thousand larvae. Some Piuropean 

 authors give the size of these ropes as three to four inches wide and 

 twelve to fourteen feet long. This habit has long been known in 

 Europe, ^nd has given the larva the names "rope-worm", "snake- 

 v/orm", and "army-worm". A few records of this habit in America 

 have appeared, the last I know of being in my paper in the preceding 

 volume of this bulletin.* 



This office has on file records of these larvae feeding upon dead 

 white-grubs that were killed by fungi or bacteria. 



Some species form a slight shiny tunnel-way in which they live, 

 but it is difficult to detect it in most cases. 



*Vol. 11, Art. TV, p. 320. (1915) 



