164 [March 



more delicate than that of the larvae of Mycetophila, whom they other- 

 wise resemble. They may be further distinguished by the structure of 

 the trophi, and most of them seem to have no bristles or spines on the 

 locomotive processes on the under side of the body, whereas the majority 

 of the Mycctophilse, have them. They are even more gregarious than the 

 other larvaj of this family, and have the singular propensity of sticking 

 together in dense patches, in which situation they are frequently found, 

 for instance, under the bark of trees. It is probably to the same propen- 

 sity that the phenomenon, known in Germany under the name of army 

 worm (Heer-wurm), is due. This is a procession of larvae, sometimes 

 from 12 to 14 feet long, and two or three inches broad, consisting of 

 numberless specimens, sticking closely together and forming a layer of 

 about half an inch thickness. Such processions has been often observed 

 in woods in Germany, Sweden and Russia, but never sufficiently investi- 

 gated to explain their object. That the larvae do not migrate in search of 

 food, we can infer from the fact that they appear to be full-grown when 

 they form these processions. (E have not seen the last pamphlet on this 

 subject, by Mr. Hohmann, published in 1857. I believe, however, that 

 it contains nothing new, as Dr. Gersfacker, in his Annual Report on the 

 Progress of Entomology, for 1858, merely mentions its publication, with- 

 out giving any extract.) 



Another remarkable fact with relation to the habits of Sciara, has been 

 discovered by Mr. Wiunertz, and published afterwards by Mr. Loew. 

 The larva of Sc. tilicola Lw., produces a gall on the leaves of young lin- 

 den trees, in shady, sheltered situations. The lemon-yellow larva, capable 

 of leaping, like the cheese-maggot, lives in numbers in the stem, generally 

 near the origin of the last or of the two last leaves. Each of them has a 

 hollow of its own, and produces a swelling of the size of a pea, which it 

 abandons before the transformation. 



The following additional account is given on the habits of Sciara fus- 

 cipes Meig., by Heeger :- "The females lay there eggs in decaying fungi 

 or vegetable mould ; the eggs form short strings, from 6 to 10 in succes- 

 sion. If the weather is favorable and the temperature modei'ate, the 

 larvae are excluded in 8 or 10 days ; they shed their skin three times, at 

 irregular intervals, depending on conditions of heat and moisture. Before 

 undergoing the pujia-state they form near the surface of the soil a little 

 barrel-shaped case, out of which the pupa extricates itself in part, before 

 the exclusion of the perfect insect." 



" The shedding of the skin and the transformations generally take place 

 in the morning; the copulation more frequently in the evening." 



