386 DIPTERA. 



more tough and resisting." The larvae of one genus sometimes 

 live gregariously with those of other genera. Thus Osten 

 Sacken found that the "larvae of Sciophila appeared in a de- 

 caying fungus only after the transformations of Mj-cetophila 

 were entirely completed. For two or three weeks the eggs of 

 the former remained apparently dormant among the bustle of 

 so many larvne of the other species." (Osten Sacken.) Leja 

 resembles Sciophila in its habits. The larvae of Sciara have 

 no bristles on the tubercles of the under side of the body, usu- 

 ally present in the famil}^ They are more gregarious than 

 the other genera, and have the singular propensity of sticking 

 together in dense patches, generall}' under the bark of trees. 

 When fully grown they sometimes marcli in processions in a 

 dense mass, sometimes several feet long, and two to three 

 inches broad, and half an inch in thickness, whence the Ger- 

 mans call them " Army-Avorms." To the same genus belongs 

 the /S. (Molobrus) mali of Fitch, the apple midge, whose larva 

 is glassy white and devours the interior of apples. 



Professor E. D. Cope describes in the Proceedings of the 

 Philadelphia Academy, 1867, page 222, a procession of a spe- 

 cies of /Sciara observed in September by William Kite, in Ches- 

 ter County, Penn., where li3 liad observed this array-woi'm for 

 three consecutive years. "This company (consisting by rough 

 estimation of about 2,400) extended over a length of about 

 twenty-two inches, with a breadth of from three-fourths of an 

 inch in the thickest part, to about one-eighth of an inch at the 

 head, and one-tenth at tail ; five or six worms deep in thicker 

 parts. They advanced at the rate of four inches in five 

 minutes, the hinder ones Avorking their way over the top of 

 the rest." These larvae were about one-half an inch long, 

 semitransparent, AA'ith black heads. Mr. Kite obserA'ed another 

 procession July 8th, which was six feet six inches long. These 

 trains were attacked by larvjB of Staphylinids, ants, dipterous 

 larvifi and other predaceous insects. Seven other persoiis in 

 this country have AAdtnessed similar trains, one of Avhich AA'as 

 observed in Lee, IMass. 



The larva of Mycetohia^ which agrees closely with that of 

 Rhyphus, is found living in putrescent sap under the bark of 

 the elm tree. We have found, through the summer, great num- 



