TEE ACTION OF LI GET, ETC. 



369 



vitalized scarlet arterial blood with the darker- 

 colored and more contaminated venous blood, 

 and still further with excrementitious matters. 

 The great truth to which we are here calling at- 

 tention has not altogether escaped the notice of 

 Mr. Wallace, who writes : " The very frequent 

 superiority of the male bird or insect in bright- 

 ness or intensity of color, even when the general 

 tints and coloration are the same, now seems to me 

 to be due to the greater vigor and activity and the 

 higher vitality of the male. The colors of an ani- 

 mal usually fade during disease or weakness, 

 while robust health and vigor add to their in- 

 tensity. 1 This intensity of coloration is most 

 manifest in the male during the breeding-season, 

 when the vitality is at a maximum." But we are 

 not aware that either Mr. Wallace or any one else 

 has fully grasped the principle laid down above, 

 or traced its numerous applications, aesthetic as 

 well as biological. 



But among the " pigment-colors " there is a 

 very great diversity in permanence due to the na- 

 ture of the colors themselves, or to that of the 

 tissues in which they inhere. Dr. Hagen divides 

 such colors into epidermal, placed in hair, in 

 feathers, and in the cbitinic exo-skeleton of in- 

 sects ; and hypodermal, situate in the softer inter- 

 nal layers of the skin. That the latter are the 

 more easily affected by any external influence is 

 natural. 



Alterations and degradations of color similar 

 to those above mentioned may, indeed, under cer- 

 tain circumstances, be produced even in the ab- 

 sence of light. But we have direct experimental 

 evidence to show that, other things being equal, 

 animal matters retain their colors most complete- 

 ly in the absence of light, and fade the more 

 rapidly in proportion to the intensity of the 

 illumination to which they are exposed. Hence 

 we are compelled to recognize light as a destroyer 

 of animal coloration. 



But light is generally regarded not merely as 

 a color-destroyer, but as a color-producer, and it 

 is with this its supposed function that we have 

 now to deal. Those who take here the affirma- 

 tive view rely mainly on two facts, or supposed 

 facts, to -which we have already briefly referred — 

 the higher coloration and the superior brilliance 

 of the tropical fauna, and the sombre hues of 

 nocturnal and subterranean beings. At these 

 facts we must look, and seek to ascertain their 



1 Those who are brought practically in contact with 

 animals hnve long been familiar with the fact that a 

 '• dull coat " is indicative of disease, or at least of 

 weakness. 



GO 



meaning. We must of course admit that Europe 

 produces no humming birds or trogons, no Be- 

 liouotce or Pachyrhynchi ; but we must also re- 

 member that the total number of species of birds, 

 of reptiles, and of insects found, say in South 

 America, is far greater than the sum total exist- 

 ing in Britain or on the European Continent. 

 Hence, even if the tendency to produce a gay 

 coloration were equal in either case, the proba- 

 bility is that South America would be the richer 

 in gorgeous species. Again, travelers who visit 

 tropical countries not unnaturally select the most 

 showy forms, and their collections are therefore 

 not a fair average. Naturalists, such as Mr. 

 Wallace, who have taken the trouble to examine 

 closely, find that even in New Guinea, Borneo, or 

 Brazil, dull-looking species exist in numbers. 

 Had we catalogues of the insects of such coun- 

 tries as complete as those we possess for Britain, 

 France, or Germany, our views as to the general 

 character of a tropical fauna would be doubtless 

 modified. As the insects of warm climates, also, 

 are upon the whole larger than those of our hyper- 

 borean latitudes, they necessarily attract atten- 

 tion, and their beauty does not pass unseen ; yet 

 every entomologist knows that even in Britain we 

 possess " tiny miracles of Nature " which, if 

 viewed with a lens of low power, display a splen- 

 dor little — if at all — inferior to the most richly- 

 attired tropical species. We will merely mention, 

 as instances, Chryseis iynita, Chrysomela cerealis, 

 Donacia protevs, Polydrusus micans and Jfavipes, 

 Rhynchites betulce undpopuli, Lampra rutilans, and 

 Anthrazia salicis. Calosoma sycophanta, also, if 

 very rare in Britain, is very common in certain 

 parts of Central Europe, and may be fairly con- 

 sidered one of the most gorgeous species of the 

 entire family of Carabidce to be met with in any 

 part of the world. 



The case, then, seems to stand thus: We 

 have in Britain certain species, small, and it may 

 be rare, which display the very same shades of 

 color and the same brilliance as we find in the 

 most admired forms of tropical life. This fact 

 seems to us scarcely consistent with the theory 

 that the more intense light of low latitudes is a 

 prominent factor in the production of splendid 

 colors. Were such the case, gayly-colored spe- 

 cies in our climate would not merely be fewer and 

 smaller ; they would rather be altogether wanting. 



Again, different portions of the torrid zone 

 differ very widely as regards the number, and 

 even the beauty, of the richly-attired birds and 

 insects they produce. Thus, as Mr. Wallace has 

 pointed out, in New Guinea 60 per cent, of the 



