INSTINCT AND INTELLIGENCE. 



hinges (fig. 6). For this purpose the animal excavates in the 



ground a sort of cylindrical shaft three or four inches deep, and 



coats its sides mth a tenacious 

 plaster. It then fahricates a door, 

 hy uniting alternately layers of 



^ja' 'S^M^I^^^ kf-— ^-^ plaster and vegetahle filaments. 



r-^C^J^HKi>^iMH^m^^ This trap-door is made exactly to 



fit the mouth of the shaft, to which 

 it is hinged by cementing some 

 ]irojecting filaments against the 

 upper edge of the plastered surface. 

 The external surface of this trap- 

 door is rough, and in its general 

 appearance differs little from the 

 surrounding ground. The inside 

 surface, howeyer, is smooth and 

 On the side opposite to the hinge there is a row 



Fig. 6.— Xt-st of the Mygalo. 



nicely finished, 



of little holes, in which the animal introduces its claws to holt 



the door when any external enemy seeks to force it open. 



26. It is, however, among the countless species of insects that 

 we find the most curious and interesting processes adopted for the 

 construction of habitations. Many species of caterpillars construct 

 houses by rolling up leaves and tying them together by threads 

 spun by the animal itself. In the gardens, nests of this kind are 

 everywhera to be seen, attached to the leaves of flowers and 

 bushes. It is in this way that the caterpillar of the nocturnal 

 butterfly, the Tortrix viridana, forms its nest (fig. 7). 



27. Other iasects construct habitations for themselves with the 

 filaments of woollen stuff, in which they gnaw holes. Among 



these is the well-known larva 

 of the common moth, popxilarly 

 miscalled a worm, which is found 

 to be so destructive to articles of 

 furniture and clothing. "With 

 '^^g-^^^jj^g^^^^^^' the woolly filaments which it 



thus cuts from the cloth, the 



caterpillar constructs a tube or 



?^^ sheath, which it continually 



lengthens as it grows. When it 



Fig. r.-Nest of Tortrix Viridana, finig jtgelf becoming too bulky 



to be at ease ia this dwelling, it cuts it open along the side, and 



inserts a piece, by which its capacity is increased. 



28. Certain animals, which pass the cold season in a state of 

 lethargy, not only prepare for themselves a suitable retreat, and 

 a soft and comfortable bed, but when they become sensible of the 



124 



