222 Insect Architecture. 



of forming a cavity is to press it with its body ; and, by 

 turning round and round for this purpose, an oblong hollow 

 is soon made. But were it left in this state, as Reaumur 

 well remarks, though the vault might endure the requisite 

 time by the viscosity of the earth alone, were no change to 

 take place in its humidity, yet, as a great number are 

 wanted to hold out for six, eight, and ten months, they 

 require to be substantially built; a mere lining of silk, 

 therefore, would not be sufficient, and it becomes necessary 

 to have the walls bound with silk to some thickness. 



When a caterpillar cannot find earth sufficiently moist to 

 bear kneading into the requisite consistence, it has the 

 means of moistening it with a fluid -which it ejects for the 

 purpose ; and as soon as it has thus prepared a small pellet 

 of earth, it fits it into the wall of the vault, and secures it 

 with silk. As the little mason, however, always works on 

 the inside of the building, it does not, at first view, appear 

 in what manner it can procure materials for making one or 

 two additional walls on the inside of the one first built. As 

 the process takes place under ground, it is not easy to 

 discover the particulars, for the caterpillars will not work in 

 glazed boxes. The difficulty was completely overcome by 

 M. Reaumur, in the instance of the caterpillar of the water- 

 betony moth (Gucullia scrophularice, SCHKANK), which ho 

 permitted to construct the greater part of its under-ground 

 building, and then dug it up and broke a portion off from 

 the end, leaving about a third part of the whole to be re- 

 built. Those who are unacquainted with the instinct of 

 insects might have supposed that, being disturbed by the 

 demolition of its walls, it would have left off work ; but the 

 stimulus of providing for the great change is so powerful, 

 that scarcely any disturbance will interrupt a caterpillar in 

 this species of labour. 



The little builder accordingly was not long in recom- 

 mencing its task for the purpose of repairing the disorder, 

 which it accomplished in about four hours. At first it pro- 

 truded its body almost entirely beyond the breach which had 

 been made, to reconnoitre the exterior for building materials. 



