388 fVilliam Morton Wheeler 



whether the percentage of this modification is so much greater 

 among stylopized than among unstylopized individuals as to 

 show that it must be attributable to the influence of the parasites. 

 I am inclined to believe, however, that it is part of a more general 

 erythri'sm which affects also the abdomen of many parasitized in- 

 dividuals. This region, to a varying degree in such specimens, but 

 undoubtedly to a greater degree in those that are most heavily 

 stylopized, takes on in both sexes alike a distinct ferruginous tinge 

 w^hich is usually most pronounced towards the posterior borders 

 of the tergites and sternites. Sometimes it may be very strongly 

 developed as in one rather small female taken August 29, and 

 bearing three male Xenos. In this case the second gastric segment 

 is entirely ferruginous, with the exception of a black anteromedian 

 triangle, and the posterior half of each of the remaining segments 

 and the whole clypeus, except its anterolateral corners, are rich 

 ferruginous. I have failed to notice in the legs, wings and antennae 

 of either sex in stylopized specin-iens any color modifications that 

 could not be regarded as falling within the wide limits of normal 

 specific variability. 



The color modification here described is not confined to styl- 

 opized specimens of P. metricus. It has also been observed by 

 Brues ('03) in two of the Texan species, P. rubiginosus and annu- 

 laris. "The stylopized Polistes," he says, ''can be recognized even 

 before the heads of the pupa cases begin to appear between the 

 sclerites of the abdomen, by their paler color. They seem never 

 to become as darkly colored as normal specimens. This lighter 

 color of parasitized specimens seems to apply only to the origi- 

 nally dark species, in P. rubiginosus there seems to be but slightly 

 if any lighter coloration. In the specimens of P. annularis from 

 which I raised Xenos, all of them females, the faded appearance is 

 especially noticeable upon the dorsum of the abdomen. The 

 first abdominal which is normally piceous with a narrow apical 

 yellow band is in this case alm.ost entirely bright ferruginous, or 

 is ferruginous with the border yellow. The remainder of the abdo- 

 men is normally piceous, but the posterior margins of the seg- 

 ments, especially the second and third tend to become more or less 

 broadly dull ferruginous in stylopized specimens." 



