ARCHITECTURE OF MOTHS. 83 



with the properties of air, it has another resource 

 when any extraordinary violence threatens to over- 

 turn its slender turret. It forms a vacuum in the 

 protuberance at the base, and this as effectually 

 fastens it to the leaf as if an air-pump had been 

 employed ! This vacuum is caused by the insect's 

 retreating, on the least alarm, up its narrow case, 

 which its body completely fills, and thus leaving the 

 space below free of air."* If one of these cases is 

 detached from the leaf, this fact may easily be per- 

 ceived. If the cell is suddenly seized, while the 

 insect is at the bottom, it will be found readily pulled 

 off, as the silken cords give way to a very slight 

 force ; but, if it is done more gently, the insect gets 

 time to retreat, in which event the case will become 

 so firmly fixed, that some force will be required to 

 remove it. " As if aware that, should the air get 

 admission from below, and thus render a vacuum 

 impracticable, the strongest bulwark of its fortress 

 would be destroyed, our little philosopher carefully 

 avoids gnawing a hole in the leaf, contenting itself 

 with the pasturage afforded by the parenchyma above 

 the lower epidermis ; and, when the produce of this 

 area is consumed, it gnaws asunder the cords of its 

 tent, and pitches it at a short distance as before."f 



When the animal attains its full growth, it assumes 

 the pupa state ; and, after its appointed period of 

 confinement, bursts its casement, and issues forth a 



* KIRBY and SPENCE'S Introduction, i. 467. 

 Ibid. 



