AMERICAN COLEOPTERA. 213 



On certain genera of Stapliylinidie 



OX\TEI.INI, PIKSTIDyH, and 9IICU0PEPI.ID.1E:, 



as represented in the fauna of the United States. 



BY JOHN L. LECONTE, M. D. 



OXYTELINI. 



Having had recent occasion to arrange the species of Bkdius in 

 my collection, I perceived the necessity of grouping them in a natural 

 manner in order to exhibit more clearly the relations between allied 

 species in difi'erent parts of the country. As many of them are found 

 only in the immediate neighborhood of the ocean-shore, or on con- 

 tiguous salt marsh, it is evident, that if allied species occur inland 

 at remote distances, they indicate the former presence of ocean water 

 in those regions, and the divergence between the two forms will enable 

 us to get some idea of the rapidity of change of structure in these 

 instances, from the time when their homogeneous ancestors were sepa- 

 rated and exposed to different influences by the progress of geological 

 changes. 



I would take occasion here to confirm the excellent remarks of Dr. 

 David Sharp on the great value of sexual characters for the separation 

 of nearly allied species in many of the genera of Staphylinidoc. I 

 know in fact, of nO other family of Coleoptera, in which forms at 

 first sight almost undistinguishable may by the study of these char- 

 acters, be most readily recognized. 



Concerning these secondary sexual characters, which in the Oxytelini 

 affect partly the head, partly the last two or three ventral segments, 

 1 have two observations to make : 



1st. That in each group containing several species allied together 

 by great natural resemblances, there will be found a gradation from 

 those in which sexual characters are strongly expressed, to those in 

 which they become trifling, or imperceptible. 



2d. That where the sexual differences are strongly expressed at one 

 extremity of the body, there is a diminution of the differences at the 

 other end; thus indicating a polar action of the organizing influence, 

 of such kind that when it manifests itself in one region of the body, 

 it is correspondingly diminished at the other. This is not of the 

 nature of correlation of growth, as ordinarily exhibited, by which an 

 organ grows by appropriation of the material which would otherwise 

 be divided between it and neighboring organs, but is more akin to 



TRANS. AMER. ENT. 80C. VI. (29) OCTOBER 1877. 



