322 



INTRODUCTION TO ZOOLOGY. 



In the former part we mentioned (p. 137), that some 

 Caterpillars spin a snow-white canopy, and dwell together in 

 social communities. Among birds we have an example of 

 their united efforts being, in like manner employed in the 

 construction of a common covering. This is observable in 

 the sociable Grosbeak (Loxia soda), a species found about 

 the Cape of Good Hope. These birds construct a roof of 

 grass matted together; and beneath the eaves of the shed 

 thus formed by their joint labour, the individual nests are 

 built (Fig. 254). Some idea of the size and solidity of these 

 structures may be formed from the fact mentioned by Vaillant,* 

 that having observed one of enormous size, he despatched 

 some men with a waggon to bring it, and on its arrival he cut 

 it to pieces with a hatchet. 



Fig. 254. NEST OF SOCIABLE GROSBEAK. 



Organs of Voice. The period when birds are about building 

 their nests, and engaged in attending to the callow young, is 

 that in which our groves become ' ' prodigal of harmony. ' ' 

 This may, therefore, be a fitting place to make some remarks 

 on the organs of voice. In birds, they consist of a wind- 

 pipe, which divides at the lower part into the two branches 

 called the bronchial tubes one leading to each lung (as shown 

 * Travels, second series, vol. iii. 



