Chap. V. BUTTEKFL1ES. 345 



Lej)idoptera, and on the ants, several kinds of which, 

 found chiefly on the Upper Amazons, exhibit the most 

 extraordinary instincts. 



I found about 550 distinct species of butterflies at 

 Ega. Those who know a little of Entomology will be 

 able to form some idea of the riches of the place in this 

 department, when I mention that eighteen species of 

 true Papilio (the swallow-tail genus) were found within 

 ten minutes' walk of my house. No fact could speak 

 more plainly for the surpassing exuberance of the vege- 

 tation, the varied nature of the land, the perennial 

 warmth and humidity of the climate. But no descrip- 

 tion can convey an adequate notion of the beauty and 

 diversity in form and colour of this class of insects in 

 the neighbourhood of Ega. I paid especial attention to 

 them, having found that this tribe was better adapted 

 than almost any other group of animals or plants, to 

 furnish facts in illustration of the modifications which 

 all species undergo in nature, under changed local con- 

 ditions. This accidental superiority is owing partly to 

 the simplicity and distinctness of the specific characters 

 of the insects, and partly to the facility with which very 

 copious series of specimens can be collected and placed 

 side by side for comparison. The distinctness of the 

 specific characters is due probably to the fact that all 

 the superficial signs of change in the organisation are 

 exaggerated, and made unusually plain, by affecting the 

 framework, shape, and colour of the wings, which, as 

 many anatomists believe, are magnified extensions of 

 the skin around the breathing orifices of the thorax of 

 the insects. These expansions are clothed with minute 



