390 Will tarn Morton Wheeler 



stylopization or indeed to insects. Janet ('03) describes and 

 figures a very similar abnormality in Vespa rufa, an insect that 

 is not afflicted with Stylops or Xenos, and Cori and Morgan ('92) 

 show that similar abnormalities are not uncommon in earthworms 

 and cestodes. In the case of Polistes the abnormality must be 

 produced either in the early embryonic stages while the metameres 

 are forming or at the time of the formation of the abdominal 

 sclerites in the pupa. 



We may conclude, therefore, that Xenos produces no modih- 

 cationsof the secondary sexual characters of its Polistes host com- 

 parable to those produced by Stylops in the bees of the genu- 

 Andrena, but merely a tendency to a reddish coloration of the 

 abdomen and face, a tendency which, so far as the abdomen is 

 concerned, v- manifested equally by both sexes. 



This general lightening of color in stylopized FoHstes and its 

 reddish tinge remind one at once of the similar changes observed 

 by Perez in Andrenae, although in the latter insects it seems to 

 be confinea to the pilosity. Pierce ('09, p. 32), cites the following 

 observations, which show that a similar change of color was long 

 ago observed by Saunders in stylopized bees of the genera Pros- 

 opis and Hylaeus: "Prosopis gibba occasionally exhibits irregular 

 rufous patches on the abdomens of affected individuals (Saunders, 

 '50). Prosopis rubicola exhibits color changes regularly. The 

 nymphs of those Hylaei which are likely to produce the pale-colored 

 specimiens (H. versicolor), which prove, as anticipated, to be only 

 a variety of the H. rubicola consequent upon parasitic absorption, 

 may usually be identified within one or two days of their final 

 metamorphosis by assuming a yellow tinge, and may be set 

 apart as certain to produce male parasites. (Saunders '52.)" It 

 is not easy to account for this modification. Brues is inclined to 

 believe that "the reason that the reddish Polistes are not affected, is 

 that red is a more primitive color than piceous and that the color 

 simply becomes arrested at this stage and does not tend to become 

 so before the red stage." The question of the developmentof varia- 

 tions of color in the species of Polistes is a very complicated one, 

 as Miss Enteman ('04) has shown, and a number of possible 

 explanations of the erythrism of stylopized individuals might be 



