PACKARD.] INSECTS AS MIMICS. 275 



Anthrenus (Fig. 213; b, larva and a, pupa, all enlarged) 

 assi;nilate in color the dried skins and decaying matter in 

 which they luxuriate. Tlie larvre 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 man}' others, when disiturbed 

 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, Avhen 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 remarkal)le changes that took 

 place to the northward ; the disappearance of an Arctic 

 continent, the replacement of a tropical climate in Green- 

 land and Spitzbergen by Arctic cold. Are there not here 

 changes enough in the phj'sical aspects of our country to 

 warrant such hypotheses of migrations with corresponding 



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