Coleopterological Notices. 417 



necessary to allow a more or less extended latitude for variation 

 in the size of the wing, especially in the more rudimentary forms, 

 where complete inutility probably prevents the operation of any of 

 the laws of natural selection, which act so powerfully to maintain or 

 perfect the standard in those organs which, by reason of constant 

 utility, are continually brought under their influence. The present, 

 however, is perhaps not the best occasion to discuss the propriety 

 of using differential characters relating to rudimentary organs ; it is 

 a subject requiring far wider study than I have been able to give it, 

 and it can only be said that any truth which the preceding hypo- 

 thesis may involve, has been guarded against by giving more weight 

 to the general shape of the wing than to size, unless the latter should 

 exhibit very decided divergence. 



2 — The vestiture varies conspicuously, but is always uniform in 

 structure. It may consist of suberect scales as in sulcatus, or of 

 hairs, more or less coarse or fine and generally subrecumbent, as in 

 the majority of species; I have allowed considerable weight as an 

 auxiliary character to decided differences in size, color and length 

 of the hairs. , 



The vestiture of insects is too often confounded with, or con- 

 sidered analogous to the hairy covering of vertebrate animals, and 

 knowing to how great an extent the latter may vary, depending 

 upon climatic conditions of environment, we are sometimes too 

 hasty in concluding that the former must vary in the same way; 

 this is, however, not the case, as a little thought will at once 

 demonstrate. 



The hairy coat of the vertebrates, growing from a soft and sensi- 

 tive skin, is designed primarily as a protection from the vicissitudes 

 of the weather, or to retain the heat which would otherwise be 

 dissipated, to regulate the rapidity of evaporation, and to perform 

 other analogous functions depending upon the fact that vertebrates 

 are warm-blooded, internal-skeletoned animals. 



In the articulates, — cold-blooded, external-skeletoned animals, — 

 the conditions are altogether different, and the vestiture, which in a 

 large proportion, for example of the Coleoptera, constitutes one of 

 the most diversified and wonderful characteristics of the organism, 1 



1 The vestiture is often extremely complicated. In Sitona, for example, it 

 is quadruplex, each of the four separate constituents probably having its own 

 sphere of utility. First there is a ground covering of wide rounded strigose 

 scales, generally densely placed, secondly a system of short robust piceous 



