222 
Psyche 
[September 
Naumann may be of interest (his nest no. 2048; see type designation 
for locality). 
This was a nest of Stelopolybia sp., a social vespid that typically 
nests in cavities. In this case the nest occupied several cavities inside 
a large carton ant nest ( Azteca sp.) attached to a tree trunk, 2 m 
above the ground. On May 7, a wasp was seen walking about on 
the surface of the ant nest. It was captured and proved to be a male 
pompilid (the type of this species). On June 21 both wasp and ant 
nest were heavily damaged by children, but on July 3 both wasps 
and ants were still active, and the nest was harvested by chloro- 
forming it and catching the contents in a sac. The three female 
pompilids were found among the vespids, the ants, and the rubble. 
Structure of the females suggests strongly that they build mud 
cells: this is the usual function of stiff bristles on the labium and a 
smooth pygidial plate. In this instance it seems probable that they 
were utilizing a part of one of the cavities inside the ant nest and 
being tolerated by the ants and the vespids. I suggest that the large 
head of the male may enable it to pass as a worker Azteca ant. 
These ants are polymorphic, and the larger workers commonly are 
macrocephalic. In this instance the workers were considerably 
smaller than the male Dimorphagenia , but they were of a similar pale 
color and the larger workers decidedly macrocephalic. Presumably 
macrocephaly does not occur in the female sex because it would 
render them unable to perform their usual hunting and nest-building 
activities. Macrocephaly in the male suggests that the male is more 
than a passive inhabitant of the nest; perhaps the presence of several 
such males inhibits attacks by ants and social wasps. One can only 
hope that the relationships of these insects can some day be worked 
out in detail. 
Genus Ageniella Banks 
Cyrtagenia, new subgenus 
Type-species. — Ameragenia fallax Aide. 
Subgeneric characters. — Females with the general features of 
Ageniella s. str. except as follows (males unknown). Mandibles un- 
usually broad, with a small tooth located close to the apex (Fig. 6) ; 
clypeus with rather sharp anterolateral corners and with a median, 
apical angulation; front, in lateral view, either abruptly subangulate 
a short distance above the antennal sockets, then flat to the vertex 
crest, or flattened all the way from the antennal sockets to the vertex 
(Fig. 7), in either case with a median prominence just above the 
