Cuap. XII. VALUE OF STUDY OF BUTTERFLIES. — 353 
exposed. It 
may be said, 
therefore, 
that on these 
expanded 
membranes 
nature writes, 
ason a tablet, 
the story of 
the modifications of species, so truly do ail changes of the 
organisation register themselves thereon. Moreover, the 
same colour-patterns of the wings generally show, with great 
regularity, the degrees of blood-relationship of the species. 
As the laws of nature must be the same for all beings, the i 
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 some day be valued 
as one of the most important branches of Biological science. 
I have mentioned, in a former chapter, the general sultry 
condition of the atmosphere on the Upper Amazons, where 
the sea-breezes which blow from Para to the mouth of the 
Rio Negro (1000 miles up stream) are unknown. This 
simple difference of meteorological conditions would hardly 
be thought to determine what genera of butterflies should 
inhabit each region, yet it does so in a very decisive 
manner. The Upper Amazons, from Ega upwards, and the 
eastern slopes of the Andes whence so large a number of 
the most richly-coloured species of this tribe have been 
received in Europe, owe the most ornamental part of their 
insect population to the absence of strong and regular 
winds. Nineteen of the most handsome genera of Ega, 
containing altogether about 100 species, are either entirely 
absent or very sparingly represented on the Lower Amazons 
within reach of the trade winds. The range of these nine- 
teen genera is affected by a curiously complicated set of Suspended 
circumstances. In all the species of which they are com- ¢°coon of 
posed, the males are more than roo to one more numerous ssp 
than the females, and being very richly coloured, whilst the females 
are of dull hues, they spend their lives in sporting about in the sunlight, 
imbibing the moisture which constitutes their food, from the mud on the 
shores of streams, their spouses remaining hid in the shades of the 
forest. ‘The very existence of these species depends on the facilities 
which their males have for indulgence in the pleasures of this sunshiny 
life. ‘The greatest obstacle to this is the prevalence of strong winds, 
which not: only dries rapidly all moisture in open places, but prevents 
the richly-attired dandies from flying daily to their feeding-places. I 
noticed this particularly whilst residing at Santarem, where the moist 
margins of water, localities which on the Upper Amazons swarm with 
these insects, were nearly destitute of them; and at Villa Nova (where 
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