50 THE INSECT WOELD. 



Reaumur saw large districts of grassy swamps in Poictou which 

 in certain years furnished very little grass for the cattle, on 

 account of the ravages caused by these larvae. They had also 

 much injured the harvest in the same districts during those 

 years. 



These larvae appear to require no other food than vegetable 

 mould. Their excrements are, in fact, according to Reaumur, 

 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 tines of the insect have withdrawn all nourishing matter.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 TipulcB often lay their eggs. Reaumur fre- 

 quently found the larvae in the trunks of elms or willows, and 

 also in the fleshy parts of certain kinds of mushrooms. He care- 

 fully observed the habits of one, which lived under the covering 

 of a mushroom, the Oak agaricus. 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. Gu^rin-Meneville has published some very interesting re- 

 marks on the migrations of the larvae of a particular kind of 

 Tipula, known 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 history 

 of insects. These small larvae 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 larvae 

 resemble some 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 



