COLORATION IN POLISTES. 37 



Passing eastward, Colorado, Kansas, and Nebraska furnish all imag- 

 inable transitions between the aurifer type and the typical variatus, 

 by which is meant the modal condition for the species in Wisconsin. 

 Specimens from southern Colorado and lower altitudes stand very close 

 to P. aurifer. Farther north and in higher altitudes the black and 

 ferruginous areas tend to increase until in all the specimens from 

 Kansas and Nebraska, which in collections are variously labeled aurifer 

 and variatus, the corresponding pattern and line could be paralleled in 

 my series of nest variations from Wisconsin. 



GENERAL CONCLUSIONS CONCERNING RELATIONS OF POLISTES VARIATUS. 



In summing up our observations on the related species we are led to 

 the conclusion that the genus Polistes is represented in the North 

 Central States by the very variable species P. variatus. Its variations 

 exhibit in the main, two trends : ( i ) Toward a conspicuously black and 

 yellow form with yellow areas large and well defined ; (2) toward a 

 black, ferruginous and yellow form, with the yellow areas largely 

 obscured by ferruginous or black. 



Southwestward representatives of the species merge into forms con- 

 sonant with the first or xanthic trend of variation ; eastward and south- 

 eastward they pass insensibly into forms more and more ferruginous, 

 or black and ferruginous. 



It is hardly probable that we have in P. variatus a primitive species 

 which has differentiated in two directions, but, as we shall see from the 

 study of the geographical distribution of the species, P. aurifer and P. 

 pallipcs are two originally distinct species which, from the course of 

 their migrations northward, have come together in the Mississippi 

 Valley, and by their commingling produced a species having in some 

 measure the characters of both. 



Related to these three species are a number of species whose validity 

 I am not prepared to deny ; but the representatives of these species, as 

 I have studied them in the large and comprehensive collections at my 

 disposal, have generally exhibited among themselves much slighter 

 range of variability than were in many cases observed in the nest 

 collections of P. variatus and P. palhpcs. These species are on the one 

 hand P. anahcimensis from California, which is plainly identical with 

 the aurifer of southern California, and P. minor, fuscatus, fuscatus insta- 

 bilis, fuscatus cxilis, and metrica. Until further detailed study can be 

 made on the nest variations and distribution of these species, we will 

 consider them in the same general group with P.pallipes, which species 

 they approach, in general, more clearly than they do P. variatus. 



