100 The American Naturalist. [February, 
Accordingly we find many nocturnal carnivorous mammals 
that are black (e. g., minks, fisher, bears) and some that are black 
and white. We also find numerous black, as well as black and 
white, birds, insects, etc., whose colors can best be explained as 
due to the influence of natural selection among protective 
nocturnal colors. The dark gray and brownish-gray colors so 
common among small nocturnal mammals, like mice, arvicole, 
moles, shrews, marsupials, etc., are highly protective at night. 
Even when these creatures are running about among green 
grass and weeds they are scarcely visible in a feeble light. 
Such colors are not at all protective in the day time, in such 
places. Moreover, such mammals usually hide in holes or 
crevices in the day time, where the color does not matter. 
Most nocturnal black, brown, and dark gray insects, like the 
ground beetles, crickets, ants, etc., unquestionably find protec- 
tion in these colors, though they are conspicuous in the day 
time. Among diurnal birds and insects there are, also, many 
cases of conspicuous and bright colors that become protective 
by moonlight and starlight, when these creatures are asleep or 
quietly resting among foliage or flowers, and most exposed to 
their nocturnal enemies. In general, it may be said that in 
all cases where black or very dark colors are strongly contrasted 
with white, yellow, or other light markings, these patterns are 
more likely to be protective at night than in the day time. 
Such colors may be due, in many cases, to other causes, but 
when no special cause for their origin can be found, they are 
probably due, in most cases, to nocturnal protective value, and 
this can be definitely ascertained by a study of the nocturnal 
habits and surroundings. 
Many of our native butterflies have bright and conspicuous 
colors which are the reverse of protective in the daytime, 
when their acute senses and active habits afford fair protection. 
But I have observed that at night, when roosting on flowers, 
their colors so blend with those of the flowers as to render them 
inconspicuous, even in good moonlight. Many species of 
Argynnis and allied genera are conspicuously marked with red, 
brown, and orange on the under side of the wings, and have 
bright silvery spots or blotches in addition, so that they are 
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