120 Chapter III. 



they disguised their nest." 1 The visual resemblance 

 between the white tree-lichens and the paper-scraps, 

 which impressed the sensitive power of perception of 

 those chaffinches explains quite naturally their seem- 

 ingly intelligent proceeding. 



He, who concurs with Darwin 2 in attributing intel- 

 ligence to birds when their actions are influenced by 

 sensitive cognition, must credit ants with a still higher 

 degree of intelligence ; for it cannot be denied that 

 birds, in building their nests, show far more specific 

 uniformity than individual variability, whereas in ants, 

 as a rule, the contrary is the case; with them the 

 "psychic plasticity" of the nest-building instinct is no 

 doubt much greater. 



Yet the chief point of excellence, which distin- 

 guishes the architecture of ants from that of birds is 

 the number of uses to which it may be put. Birds 

 build nests to serve as places for hatching their young 

 only; except during the pairing season, birds do not 

 know their nests, nor does it ever occur to them to 

 use them as dwelling-places. With ants, however, 

 nests serve as permanent abodes for the whole family 

 and often also for strangers of different species, which 

 are hospitably received as guests. Finally, ants use 

 their architectural skill for many other purposes. But 

 before entering into particulars on this head, we would 

 like to draw a comparison between the architecture of 

 mammals and that of ants. 



In as far as the buildings of many mammals are 



J ) Ch. Darwin, too, mentions already a nest of a chaffinch described 

 by Hewitson, in which, instead of lichens, shreds of paper likewise 

 had been employed (1. c., p. 417). 



2 ) L. c., p. 414. 



