1966] 
Evans — Female Plumarius 
233 
(apical) segment rather broad, simple, non-setose, giving rise to an 
apparently rather short sting. 
Comments on characters of , male Plumarius. — Evidence that the 
females just described represent the opposite sex of nocturnal males 
of the genus Plumarius may be summarized as follows: (1) both 
males and females are of generally light brown coloration; (2) 
Peruvian males I have seen are of about the size one would predict 
for males of the wasp described above; (3) both sexes have erect 
setae on the antennae, although these are much more abundant in 
the male; (4) the labium is very similar, the labial palpi 3-segmented 
in both sexes (much as in Fig. 6) ; (5) in both sexes the mandibles 
are tridentate, the teeth thickened and heavy, and the mandibles 
have numerous setae and sensilla; (6) the labrum of the male is 
small, bristly, and mostly or wholly concealed by the clypeus, though 
in general more narrow than in the female; (7) in both sexes the 
prosternum is very large, and there is a partially differentiated 
sclerite just in front of the anterior coxae which probably represents 
the proepimeron (Figs. 11 and 12); (8) all coxae are subconical, 
and the members of each pair are contiguous or nearly so; (9) the 
mesopleura are strongly swollen; (10) there is no constriction be- 
tween the first two metasomal sternites. 
In spite of these many similarities, the males are radically dissim- 
ilar to the females in many features: they have large eyes and ocelli, 
the wings are fully developed, and the thorax is without the many 
reductions associated with flightlessness; the maxillary palpi are 
much longer and have six segments rather than five; the face and 
clypeus are unusually elongate; the abdomen is sessile; and of course 
there are the usual differences in the form of the abdomen and in 
the genitalia. On the whole the sexual dimorphism is no greater than 
one has learned to expect in certain Tiphiidae (Brachycistidinae, 
Thynninae) or Bethylidae (Pristocerinae) . 
In the effort to determine the correct systematic position of the 
Plumariidae, it seemed desirable to make a preliminary study of the 
terminal segments of the male abdomen, since the family was omitted 
by Snodgrass (1941) and others who have studied the male genitalia 
of Hymenoptera. The apical tergite (Fig. 14) is of generalized 
structure and bears pygostyles much longer than any known in the 
Bethylidae, though not dissimilar to those of certain Mutillidae and 
Formicidae (Snodgrass, 1941, plates 13, 14). The apical sternite 
(Fig. 13) is a simple, tongue-shaped structure similar to that of 
certain Formicidae or Bethylidae, and quite unlike the pseudosting 
of most Scolioidea. The genitalia (Fig. 15) are of basically simrde 
