The Zoologist — September, 1868. 1359 



They are even more gregarious than the other larvae 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 propensity that the pheno- 

 menon known in Germany under the name of army worm (heerwurm), 

 is due. This is a procession of larvae, sometimes from twelve to 

 fourteen feet long, and two or three inches broad, consisting of number- 

 less specimens, sticking closely together, and forming a layer of about 

 half an inch in thickness. Such processions have been often observed 

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

 investigated 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. 



Prof. Berthold, of the University of Gottiugen, gives a more detailed 

 account of this larva,* as follows : — 



"Mr. Berthold imparted, on the 17th of December, 1853, to the 

 Royal Society of Sciences, a zoological examination of the heerwurm 

 (army worm), which in certain years in the forests of Thuringia, 

 Hanover, Sweden and Norway, moves like a snake several feet long, 

 four to six inches broad, and thumb thick, which consists of myriads 

 of small dipterous larvae, four to five lines long. Eight years ago 

 (Reports from the G. A. University and the Royal Society of Sciences 

 at Goltingen, 1845, No. 5), he stated that the Tipula which was 

 observed by the forest keeper, Mr. Raude, at Birkenmoor, was the 

 Thomastrauer gnat [Sciara T/wmce), and was the means of solving a 

 problem, which has been for hundreds of years a returning stimulus of 

 bigotry and fear for the peasants, and for zoologists a point of earnest 

 consideration. But when he obtained last summer from the Eilenriede, 

 near Hanover, more new heerwurm larvae, and Mr. L. Bechstein bred 

 some flies out of the larvae of a heerwurm, it gave him occasion to 

 institute further examinations. 



" The desire for association and migration cannot be compared with 

 the migrations of all other insects and animals ; for this is not done to 

 procure nourishment, because the maggots are in such great quantity 

 above each other, that but few would have a chance to reach the food. 

 Also, the maggots do not show the desire for travelling immediately 

 after leaving the egg, like mauy other insects, but the movement 

 commences when the worm is grown, and not less than three lines 



* Nacbiichten Univ. Gottingen, 1854, p. 1. 



