Chap. V. BUTTERFLIES. 345 
Lepidoptera, 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 Kttle 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 
