162 Journal New York Entomological Society. [Voi. xxvi. 



association with her mate. In the eastern and southern parts of the 

 country the species are very constant as to color but on the Pacific 

 coast certain of them are very plastic. Some are truly dichromatic, 

 with the two color phases in the same territory. Others have their 

 different color varieties in different though adjacent territories, true 

 color races, while still others have intermediate as well as the ex- 

 treme color phases within the same territory and are thus only varia- 

 ble species. This color plasticity is no doubt due to climatic influ- 

 ences for other groups of Coleoptera within the same region share 

 it, such as Pedilus (Corphyra) and certain of the Elateridse such as 

 some Athoits, Limonms and Agriotes. The lighter colored phases 

 are generally to be found in the warmer lowlands while the darker 

 are more restricted to the cooler coastal areas and the high moun- 

 tains. Another peculiarity with regard to the distribution of this 

 genus is that many of the more or less isolated mountain ranges of 

 the southwest are apt to have their own distinctive species. 



The genus as now constituted is world wide in its distribution. 

 There are, however, certain groups which seem to be more or less 

 definitely restricted to certain localities. With us, the species of the 

 more typical part of the genus, those with the prothoracic armature 

 about or close to the posterior angles, are dominant on the Pacific 

 Slope, but three species being found in the more northern or moun- 

 tainous part of the Eastern States. Those which belong to the sub- 

 genus Diteninus and have the prothoracic armature distinctly in front 

 of the posterior angles, are more southern as a rule in their distri- 

 bution and quite closely related as a group to those in Mexico and 

 farther south. As to color, the members of this latter group are gen- 

 erally bicolored, but one species in our fauna being entirely black, 

 and quite constant as far as our species are concerned. 



The prothoracic armature in general is formed by a portion of 

 the posterior part of the lateral margin of the prothorax being in- 

 cised and bounded in front by an angular process or an extension 

 outwards of the same in the form of a lobe, and bounded posteriorly 

 by another process which projects outwardly from the side itself or 

 from just beneath. This latter may be in the form of a spine, a lobe, 

 or a broad plate, sometimes so large as to completely fill up the 

 incisure. The inner surfaces of these lobes are usually fringed with 

 fine erect hairs. The construction of this body varies with each 



