COLORATION IN POLISTES. 



25 



By inspection, the conditions of this surface, the second segment 

 taken as standard, were found to fall into three main classes: (A) 

 Lateral spot absent; (B) lateral spot becoming obsolete (very small, 

 brown or yellow); (C) lateral spot large, yellow, or yellow with fer- 



rugmous margins. 



Distribution of specimens in main classes. 



Lot I, Class C, have spot ferruginous or dark fuscous. 



Lot 2, Class C, have 24 specimens with spot ferruginous, 17 specimens 

 with spot yellow, 5 specimens with spot yellow, ferruginous margined. 



From this it is plain that in general the melanism of the ventral 

 surface is in advance of that of the dorsal, but those specimens which 

 possess a markedly xanthic dorsal surface also have a large amount of 

 yellow on the ventral surface. (For graphic representation of this 

 relation see fig. 12.) 



For the correlation in the case of the males Lots i and 2 were selected 

 the same as before. The classes were made with reference to the con- 

 dition of the yellow central area of second segment : (A) Central 

 area obsolete ; (B) central area reduced ; (C) central area large, in 

 form of rectangle. 



The distribution of material in the foregoing classes is shown as 

 follows : 



This shows that though there is a marked tendency toward a 

 xanthic condition for both light and dark males, this tendency expresses 

 itself more strongly in the light than in the dark ones. There is thus 

 positive correlation between the condition of the dorsal and ventral 

 sides of abdomen in both male and females. 



