50 THE INSECT WORLD. 
on account of the ravages caused by these larve. ‘They had 
also much injured the harvest in the same districts during those 
years. 
These larve appear to require no other food than vegetable 
mould. Their excrements are, in fact, according to Réaumur, 
nothing else than dried earth, from which the stomach and intes- 
tines of the insect have withdrawn all nourishing matter. 
Old trees have often hollow cavities occasioned by the decay 
of the trunk. When these cavities are old, their lower parts are 
full of a sort of mould which is in fact half-decayed wood. It is 
there that the Tipule often lay their eggs. Réaumur frequently 
found the larve in the trunks of elms or willows, and also in the 
fleshy parts of certain kinds of mushrooms. He carefully observed 
the habits of one, which lived under the covering of a mush- 
room, the Oak agaric (Agaricus quercinus). This larva is round, 
grey, and resembles an earth-worm. It does not walk, but 
crawls; and the places where it stops, or which it passes over, are 
covered with a sort of brilliant slime, like that left by the snail 
or slug. 
M. Guérin-Méneville has published some very interesting re- 
marks on the migrations of the larve of a particular kind of 
Tipula, kvown by the name of Sciara. We will borrow from 
that entomologist the following curious details, which will initiate 
us into one of the most wonderful phenomena in the whole his- 
tory of insects. ‘These small larva are without feet, hardly five 
lines in length, and about the third of a line in diameter. 
They are composed of thirteen segments, and have small black 
heads. 
In some years, during the month of July, may be found on the 
borders of forests in Norway and Hanover, immense trains of 
these larvae, formed by the union of an innumerable quantity fixed 
to each other by a sticky substance. These collections of larvz 
resemble sume sort of strange animal of serpent-like form, several 
feet long, one or two inches in thickness, and formed by the union 
of an immense number, which cling to each other by thousands, 
and move on together. The whole society advances thus with 
one accord, leaving a track after it on the ground, as a material 
indication of its presence. 
