74 COLORATION IN POLISTES. 



species, but at any rate along the Pacific coast they show the same 

 gradations in coloring as does Polistes. 



Thus species of the genus Ancestroceris from California and Nevada 

 have the characteristic black and yellow pattern, and in the species 

 from Vancouver the yellow areas are greatly reduced. In the genus 

 Pterocheilus, biplagiata shows the yellow borders broad, and conspicuous 

 yellow spots, while morrisonii from Nevada shows the yellow areas 

 somewhat reduced. An extensive series of Eumenidae (undetermined) 

 in the Philadelphia Museum and a large number of Odynerii from 

 California illustrate this same law. 



On the Florida side the genus Slossonse exhibits the carolinus type 

 of marking ; the same is true of Eumcncs smithi. De Saussure (24) 

 gives the type with yellow metameric spots as characteristic for the 

 United States and Europe, and further adds that " besides this, there 

 is produced in the southern United States another type mixing with 

 this, but characterized by a preponderance of red and suffused yellow. ' ' 

 These two forms thus bear the same relation to each other that P. 

 variatus and P. carolinus do. 



Tropical Africa, again, shows a tendency toward uniformity of species 

 along with uniformity of climatic conditions, while the East Indies 

 offer an apparent anomaly by possessing, in addition to the orange and 

 black carolinus type,- one which resembles aurifer as much as it does 

 versicolor. 



We may thus consider the great trend of development in the genus 

 Polistes as determined by general climatic conditions, while the slighter 

 differences are due to slight differences in environmental conditions, 

 operating of course on slight initial differences in the types for various 

 nests. Keeler (14) supports these ideas in his evolution of land birds. 

 He gives his testimony that moist seacoast climates produce rather 

 darker and duller hues than normal. ' ' The maximum of sunlight and 

 moisture together forms the most pure and brilliant coloration, sunlight 

 without moisture has a tendency to burn and bleach, while moisture 

 without sunlight produces darker and duller colors." In any given 

 region the coloration, while adhering to one general mode, may change 

 to a varying extent in certain directions, owing to the differences in 

 station of various forms and their comparative isolation from one 

 another. Here the inbreeding in the same nest or neighboring colonies 

 would tend to accentuate a particular line of variation. 



