Effects of Castration iti Insects 3^7 



abdomen is decidedly shorter. The antennae are 12-jointed, with 

 a shorter funiculus slightly enlarging towards its tip; the second 

 funicular joint is nearly as long as the three succeeding joints taken 

 together. The face is decidedly shorter than that of the male, 

 the grooves and welt much less pronounced and the clypeus is 

 convex and coarsely punctate. The face is black, with the internal 

 orbit and sometimes portions of the clypeus, the anterior surface 

 of the scape and of the two first funicular joints, the anterior 

 surfaces of the tibiae and apical portions of the femora, ferruginous. 

 The sulphur yellow is restricted to the tarsi and the posterior 

 border of the first abdominal tergite, and the ferruginous spots 

 on the first abdominal segment are obscure or wanting. The 

 wings are often somewhat more deeply infuscated than in the 

 male. 



In stylopized Polistes metricus of either sex I fail to find any 

 modifications of a morphological character which could be 

 definitely attributed to the presence of the parasites. A few of 

 the more heavily stylopized females were abnormally small, but 

 with these exceptions, all the wasps were of normal stature. No 

 modifications of the antennae nor of the structure and proportions 

 of the face could be detected. A study of the coloration, however, 

 yielded more positive results, but even here, owing to the great 

 range of color variation to which P. metricus like all our other 

 species of the genus, is subject, the results are not capable of very 

 precise formulation. In the coloration of the face stylopized 

 males show no tendency to approach the female. In 14 out of 25 

 heavily stylopized females I find the clypeus of the usual black 

 or dark brown color; in the remaining 11 it is more or less ferru- 

 ginous or yellow. Some specimens have the free border of this 

 sclerite sulphur yellow or its whole surface ferruginous, or only 

 its posterior border or sides of this color. One specimen has the 

 clypeus ferruginous with a small black spot in the center. It 

 would be possible to regard these cases as approximations to the 

 male type of coloration due to parasitism, were it not that per- 

 fectly normal, unstylopized females not infrequently exhibit the 

 same erythrism of the clypeus. I have not seen a sufficient num- 

 ber of P. metricus from different localities to be able to determine 



JOURNAL OF EXPERIMENTAL ZCOLOGY, VOL. 8, NO. 4 



