244 C. T. BRUES, 
all of my captives been parasitized, perhaps some more healthy in- 
dividual would have taken it upon itself to get rid of the Xenos. 
This would also be a dangerous assumption and one not borne out 
by analogy. Among the ants, a group in which the social instinct is 
much more highly developed than in Polistes, it is generally agreed 
that a spirit of coöperation which would extend to ridding one another 
of noxious ectoparasites does not exist. I have no doubt that the 
explanation lies in the fact that the males do not attempt to approach 
Polistes not containing mature females. 
The Polistes were kept under observation until they died, which 
was shortly after the last of the parasites had emerged. The death 
of the Polistes seems indeed to be in some way conditioned by their 
hatching. Whether the presence of the parasites exerts an influence 
upon the vitality of the wasp, whether the air acting through the 
spaces left by the emerging beetles dries up the internal organs or 
whether the approaching death of the host hastens the development 
of the parasites, would be hard to say. From the condition of the 
dead Polistes, I think the access of air drying up the internal organs 
is the immediate cause of death. However this may be, it seems a 
general rule that all the Xenos from one specimen of Polistes emerge 
during two or at most three mornings‘), although from the four 
specimens of Xenos they continued to appear for about a week. 
The time required for the males to reach maturity after the wasp 
emerged varied from about ten to seventeen days, the pupa cases not 
being protruded between the abdominal segments of the host until 
several days after the latter left its pupal cell, the stylopized Polistes 
can be recognized even before the heads of the pupa cases begin to 
appear between the sclerites of their abdomens, by their paler color 2). 
They seem never to become as darkly colored as normal specimens *). 
This lighter color of parasitized specimens seems to apply only to the 
originally dark species, in P. rubiginosus there seems to be but slightly 
if any lighter coloration. In the specimens of P. annularis from which 
1) The males invariably emerge early in the morning, usually 
before 9 o'clock A. M. 
2) The protruded end of the male pupa case usually becomes 
darkly pigmented immediately after or even before protrusion, as I 
have never observed but one which was light colored after it became 
visible from the outside. 
3) The color change and distortion of the abdomen can be seen 
from the accompanying photograph (Fig. A). 
