11 ANIMAL LIFE IN THE TROPICAL FORESTS 277 
or upon fully exposed leaves. Being uneatable they have no 
enemies and need no concealment. Day-flying moths of 
brilliant or conspicuous colours are also comparatively abund- 
ant in the tropical forests. Most magnificent of all are the 
Uranias, whose long-tailed green-and-gold powdered wings 
resemble those of true swallow-tailed butterflies. Many 
Agaristidee of the East are hardly inferior in splendour, while 
hosts of beautiful clearwings and Atgeriide add greatly to 
the insect beauty of the equatorial zone. 
The wonderful examples afforded by tropical butterflies of 
the phenomena of sexual and local variation, of protective 
modifications, and of mimicry, have been fully discussed 
elsewhere. For the study of the laws of variation in all its 
forms, these beautiful creatures are unsurpassed by any class 
of animals, both on account of their great abundance, and the 
assiduity with which they have been collected and studied. 
Perhaps no group exhibits the distinctions of species and 
genera with such precision and distinctness, due, as Mr. Bates 
has well observed, to the fact that all the superficial signs of 
change in the organisation are exaggerated, by their affecting 
the size, shape, and colour of the wings, and the distribution 
of the ribs or veins which form their framework. The minute 
scales or feathers with which the wings are clothed are coloured 
in regular patterns, which vary in accordance with the slightest 
change in the conditions to which the species are exposed. 
These scales are sometimes absent in spots or patches, and 
sometimes over the greater part of the wings, which then 
become transparent, relieved only by the dark veins and by 
delicate shades or small spots of vivid colour, producing a 
special form of delicate beauty characteristic of many South 
American butterflies. The following remark by Mr. Bates 
will fitly conclude our sketch of these lovely insects. “It 
may be said, therefore, that on these expanded membranes 
Nature writes, as on a tablet, the story of the modifications of 
species, so truly do all the changes of the organisation register 
themselves thereon. And as the laws of Nature must be the 
same for all beings, the conclusions furnished by this group 
of insects must be applicable to the whole organic world ; 
therefore the study of butterflies—creatures selected as the 
types of airiness and frivolity—instead of being despised, will 
