290 INSECT ARCHITECTURE. 



is left. But in this case they take no precaution of 

 strengthening the outward defence, but leave it in 

 such a state as to deceive an eye unaccustomed to 

 see trees thus gutted of their insides; and "you 

 may as well," says Mr Smeathman, " step upon a 

 cloud." It is an extraordinary fact, that when these 

 creatures have formed pipes in the roof of a house, 

 instinct directs them to prevent its fall, which would 

 ensue from their having sapped the posts on which 

 it rests; but, as they gnaw away the wood, they fill 

 up the interstices with clay, tempered to a surprising 

 degree of hardness; so that, when the house is 

 pulled dovv'n, these posts are transformed from wood 

 to stone. They make the walls of their galleries of 

 the same composition as their nests, varying the 

 materials according to their kind: one species 

 using red clay, another black clay, and a third a 

 woody substance, cemented with gums, as a security 

 from the attacks of their enemies, particularly the 

 common ant, which, being defended by a strong, 

 horny shell, is more than a match for them; and 

 when it can get at them, rapaciously seizes them, 

 and drags them (o its nest for food for its young 

 brood. If any accident breaks down part of their 

 walls, they repair the breach with all speed. Instinct 

 guides them to perform their office in the creation, 

 by mostly confining their attacks to trees that are 

 beginning to decay, or such timber as has been se- 

 vered from its root for use, and would decay in time. 

 Vigorous, healthy trees do not require to be de- 

 stroyed, and, accordingly, these consumers have no 

 taste for them.* 



M. Adanson describes the termites of Sen'^gnl as 

 constructing covert ways along the surface of wood 

 whidh they intend to attack; but though we have no 



* gmaathiiiaii. 



