296 HABITATIONS OF INSECTS. 



from the egg. As it increases in size, it enlarges its habitation by slitting 

 it in two, and introducing a strip of new materials, ^ut the most curious 

 circumstance in the history of this little Arab is the mode by which it 

 retains its tent in a perpendicular posture. This it effects partly by 

 attaching silken threads from the protuberance at the base to the surround- 

 ing surface of the leaf. But being not merely a mechanician, but a pro- 

 found natural philosopher, well acquainted with the properties of air, it 

 has another recourse when any extraordinary violence threatens to overturn 

 its slender turret. It forms a vacuum in the protuberance at the base, and 

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

 ployed ! 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. In detaching one of these cases you may 

 easily convince yourself of the fact. If you seize it suddenly while the 

 insect is at the bottom, you will find that it is readily pulled off, the silken 

 cords giving way to a very slight force ; but if, proceeding gently, you 

 give the insect time to retreat, the case will be held so closely to the leaf 

 as to require a much stronger effort to loosen 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 philoso- 

 pher 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. Having 

 attained its full growth, it assumes the pupa state, and after a while issues 

 out of its confinement a small brown moth, with long hind legs, the Pha- 

 lana Tinea serratclla of Linne.^ 



Some larvaD, which form their covering of pure silk, are not content 

 with a single coating, but actually envelop themselves in another, open on 

 one side, and very much resembling a cloak ; whence Reaumur called 

 them " Teignes a fourrcau a mantcauJ' What is very striking in the 

 construction of this cloak is, that the silk, instead of being woven into one 

 uniform close texture, is formed into numerous transparent scales over- 

 wrapping each other, and altogether very much resembling the scales of a 

 fish." These mantel-covered cases, one of which I once had the pleasure 

 of discovering, are inhabited by the larva of a little moth apparently first 

 described by Dr. Zincken genannt Sommer, who calls it Tinea paUiatella? 



Various substances besides silk are fabricated into habitations by other 

 larvae, though usually joined together either with silk or an analogous 

 gummy material. Thus Diurnca 1 lichenum forms of pieces of lichen a 

 dwelling resembling one of the turreted Helices, many of which I observed 

 in June, 1812, on an oak in Barham. The larva of another moth, which 

 also feeds upon lichens, instead of employing these vegetables in forming 

 its habitation, composes it of grains of stone eroded from the walls of 

 buildings upon which its food is found, and connected by a silken cement. 

 These insects were the subject of a paper in the Memoirs of tiie French 

 Academy'', by M. de la Voye, who, from the circumstance of their being 



' Gueze, Natur. Menschenhben und Vurschung. Anderson's Recreations, ii. 409. See 

 above p. 12. 

 » Reaum. iii. 206. ' Germar's Mag. fur Entomologie, i. 40. * x. 458. 



