78 COLORATION IN POLISTES. 



(8) Spectroscopic analysis and numerous parallel reactions suggest 

 a relation between the pigments of Polistes and a series of organic 

 pigments known as the azo-color compounds. 



(9) The pigments appear to be elaborated from the protoplasm of 

 the hypodermal cells, which in turn seems to be modified in a definite 

 manner by surrounding metabolic processes, particularly those accom- 

 panying the development of muscle. 



(10) These metabolic processes or the products elaborated by their 

 agency are further affected by external conditions such as temperature 

 and humidity, and thus varying climatic influences determine the 

 coloration of the wasp. 



(n) The individuals of the same colony vary greatly among them- 

 selves, but the variation is continuous and in certain definite directions 

 which in some cases at least can be traced to the varying external 

 conditions. 



(12) There is extensive intergradation between the numerous species 

 of the genus, which again bears a relation to climatic conditions of the 

 region where the types occur. 



(13) In any given locality the race differentiation may be accounted 

 for on the principle of segregation and slight differences in external 

 conditions. 



(14) For the larger geographical areas the type of coloring is in 

 the main due to climatic conditions in conjunction with cumulative 

 segregation. 



