22 SOCIAL LIFE IN THE INSECT WORLD 



softest mould, could form no possible part of its diet. 

 But is not the material detached simply thrust back 

 behind the excavator as the work progresses ? 



The Cigale passes four years under ground. This long 

 life is not spent, of course, at the bottom of the well I 

 have just described ; that is merely a resting-place 

 preparatory to its appearance on the face of the earth. 

 The larva comes from elsewhere ; doubtless from a 

 considerable distance. It is a vagabond, roaming from 

 one root to another and implanting its rostrum. When 

 it moves, either to flee from the upper layers of the 

 soil, which in winter become too cold, or to install itself 

 upon a more juicy root, it makes a road by rejecting 

 behind it the material broken up by the teeth of its picks. 

 That this is its method is incontestable. 



As with the larvae of Capricornis and Buprestes, it is 

 enough for the traveller to have around it the small 

 amount of free space necessitated by its movements. 

 Moist, soft, and easily compressible soil is to the larva of 

 the Cigale what digested wood-pulp is to the others. It 

 is compressed without difficulty, and so leaves a vacant 

 space. 



The difficulty is that sometimes the burrow of exit 

 from the waiting-place is driven through a very arid soil, 

 which is extremely refractory to compression so long as 

 it retains its aridity. That the larva, when commencing 

 the excavation of its burrow, has already thrust part of 

 the detached material into a previously made gallery, now 

 filled up and disappeared, is probable enough, although 

 nothing in the actual condition of things goes to support 

 the theory ; but if we consider the capacity of the shaft 

 and the extreme difficulty of making room for such a 



