34 



COLORATION IN POLISTES. 



nous is entirely absent to a large class where the yellow borders are 

 entirely obsolete excepting in the first segment. In the maximal 

 melanic condition the abdomen is entirely black. Accordingly we find 

 the material distributed in the following classes : (i) Large amount of 

 ferruginous, borders variable, 13 females; (2) Ferruginous reduced, 

 borders variable, 40 (29 females, 11 males) ; (3) Ferruginous absent, 

 yellow present in more than first segment, 8 ; (4) Ferruginous absent, 

 yellow present only in first segment, 32 (31 females, i male) ; (5) 

 Abdomen entirely black, 7. 



The collection of 100 P. pallipes from a single nest shows the same 

 stages, but in addition a number possess a prominent lateral spot which 

 is yellow or yellow edged with ferruginous. If we call these two types 

 — r and o respectively, and preserve the values for the remaining classes 

 as above defined, we find the nest variations distributed among the 

 seven classes as follows : 



Both collections give curves with two modes, and the modes fall in 

 the same classes, namely, 2 and 4. Moreover, the males again show 

 themselves more aberrant than the females. The diversity is so great 

 that we might think we were dealing here with two species did not 

 the single nest give us exactly the same types of coloration as does the 

 random collection, with an even greater range of variabiHty. 



In this species again we find the ventral surface of the abdomen 

 more melanic than the dorsal. Classes 4 and 5 are entirely melanic. 

 Class 3 has narrow, interrupted, yellow borders on the anterior seg- 

 ments. In class 2 ferruginous is often present in the form of a small 

 dot at the posterolateral angle of the segment. In class i ferruginous is 

 usually present, but always in smaller amount than on the dorsal side. 



Markings of the thorax.— As should be expected from the slight 

 amount of yellow in the abdomen, we find the yellow of the thorax 

 correspondingly reduced. The lateral spots of the metathorax are 

 entirely absent and the median stripe greatly narrowed and sometimes 

 obsolete. These median stripes vary somewhat in width, but in very 



