COLORATION IN POLISTES. 73 



prominent brownish or brown and yellow lateral spots, and where cool 

 and saturated the coloration was produced by a diffused dull-brown 

 pigment present in large quantity. Here we see that moisture tends 

 to a suffused coloration with tendency to a reddish cast of pigment, dry- 

 ness to a duller brown. Cold produces great amount of pigment, heat 

 little — and thus the tendency is to a restricted and dull brown color 

 or a diffuse and dull brown color, according as moisture is lacking or 

 abundant. 



Types of Coloration in Related Genera. 



The most striking confirmation of these tendencies, however, is 

 afforded by the colors displayed in other genera of the Vespidse. 

 Polybia, the slender thread-waisted social wasp, from which Polistes 

 has, in all probability, sprung, is peculiar to the tropics of the New 

 World and reaches its highest development in South America. It 

 presents all the color variations displayed by the Polistes of South 

 America, but only two forms have made their way into the United 

 States. These are P. cubemis of Florida and P . flavitarsis oi California. 

 In its color and markings the former corresponds exactly to the Polistes 

 of Florida, while the latter is identical with P. atiriferoi California. 



The genus Icaria is the representative of Polybia in the Old World. 

 Here the j^ellow forms, socialistica and cabetu, occur in Tasmania ; the 

 melanic form, gzittatipennis , is obtained from Senegal. Madagascar has 

 two green species peculiar to itself, and as this is the only instance of 

 the occurrence of green throughout the family, it certainly speaks for 

 the effect of isolation in originating and maintaining a species. Be- 

 lonogaster, which is the only other social wasp besides Vespa found in 

 the Old World , is peculiar to Africa. It is a notable fact that in its type 

 of marking it follows very closely the Polistes of the various sections. 

 Thus B.junceas, which is found in equatorial Africa, resembles P. 

 palUpes in its coloration. B. griseas, filvcntris, madccassa, and gzicrinii 

 all resemble canadensis ; the first two forms occur in Senegal, the two 

 latter in Madagascar. In this connection it will be remembered that 

 the only Polistes found in Madagascar is a cajiadensis having a slightly 

 smaller head than the normal. In the East Indies indiciis belongs to 

 the carol inns type. 



Among the Eumenidse, which are the solitary wasps from which the 

 social wasps had their origin, we find good illustration of the same 

 general laws, although the habits and instincts here are so various that 

 we would hardly expect this concord. 



Septentrional Eumenidae are usually of a black color varied with 

 yellow. I have not studied the variations in all these black and yellow 



