60 The Naturalist in La Plata. 



plantation adjoining my house I found, during the 

 season, no fewer than seventeen nests. 



The season was also favourable for mice ; that is, 

 of course, favourable for the time being, unfavour- 

 able in the long run, since the short-lived, undue 

 preponderance of a species is invariably followed 

 by a long period of undue depression. These pro- 

 lific little creatures were soon so abundant that the 

 dogs subsisted almost exclusively on them ; the 

 fowls also, from incessantly pursuing and killing 

 them, became quite rapacious in their manner; 

 whilst the sulphur tyrant-birds (Pitangus) and the 

 Gruira cuckoos preyed on nothing but mice. 



The domestic cats, as they invariably do in such 

 plentiful seasons, absented themselves from the 

 house, assuming ail the habits of their wild con- 

 geners, and slinking from the sight of man even of 

 a former fireside companion with a shy secrecy in 

 their motions, an apparent affectation of fear, almost 

 ludicrous to see. Foxes, weasels, and opossums 

 fared sumptuously. Even for the common armadillo 

 (Dasypus villosus) it was a season of affluence, for 

 this creature is very adroit in capturing mice. This 

 fact might seem surprising to anyone who marks 

 the uncouth figure, toothless gums, and the motions 

 anything but light and graceful of the armadillo ; 

 and perhaps fancying that, to be a dexterous mouser, 

 an animal should bear some resemblance in habits 

 and structure to the felidae. But animals, like men, 

 are compelled to adapt themselves to their surround- 

 ings ; new habits are acquired, and the exact co- 

 relation between habit and structure is seldom 

 maintained. 



