Packard.] 
INSECTS AS MIMICS. 
275 
Anthrenus (Fig. 213 ; b , larva and a, papa, all enlarged) 
assimilate in color the dried skins and decaying matter in 
which they luxuriate. The larvae especially are so densely 
clothed with gray or reddish brown hairs, that it is difficult 
to detect them when at work in dried insects and bird skins. 
Their" stealthy ways also favor their protection, and these 
beetles, like the weevils and many others, when disturbed 
feign death. 
How this mimicry of death so common among insects 
came to be such a universal habit would form a curious sub¬ 
ject of inquiry. It can scarcely, perhaps, be regarded as 
anything more than instinctive in the insects of the present 
day, but in the earlier ages of the world, when the insects 
were schooling themselves in the arts of life, such acts as 
these must have been in a degree conscious, and only became 
habitual after many mistakes and trials, resulting in the 
extinction of many individuals and incipient species. When 
one looks at the beds of fossil beings of the earlier geologic 
periods, he peers into the tombs of millions which could not 
adapt themselves to their constantly changing surroundings. 
No fossil being is known to us which could not have been 
as well adapted to its mode of life as the animals now 
living; but the conditions of life changed, and the species 
as such could not withstand the possible influx of new forms 
due to some geological change which induced emigration 
from adjoining territories, or to changes of the contour of 
the surface, with corresponding climatic alterations. Let 
one look at the geological map of North America before the 
Cretaceous period, ere the Rocky Mountains appeared above 
the sea, and reflect on the remarkable changes th&t took 
place to the northward; the disappearance of an Arctic 
continent, the replacement of a tropical climate in Green¬ 
land and Spitsbergen by Arctic cold. Are there not here 
changes enough in the physical aspects of our country to 
warrant such hypotheses of migrations with corresponding 
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