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[Vol. 95 
additional alienus specimens from Costa Rica in the collection of 
the Snow Entomological Museum were seen; these have identical 
collection data to the one in the British Museum and are labelled as 
“from nest #CR 04” and “Det. Starr, 1981.” Finally, another speci- 
men of fraudulentus from the collection of the Museum of Natural 
History of the University of Georgia was examined. This was col- 
lected in Costa Rica (“Sirena, Corcovado Nat. Pk., Puntarenas 22- 
III- 1981, C. K. Starr, nest series no. 204”), determined as 
“? fraudulentus ” by Richards, and was accompanied by a nest. 
M. alienus is distinguished from pelor by its larger size (forewing 
length 9.5-10.6 mm), less asymmetrical third segment of the mid 
and hindtarsi (Fig. 4), and nest (see below), but is similar in having 
the propodeal longitudinal carina dorsally effaced. The enlarged 
hindclaw is usually narrower in alienus (Fig. 4), but this feature 
varies somewhat. M. fraudulentus is more similar to pelor: the third 
segment of the mid and hindtarsi is similarly asymmetrical and the 
enlarged hindclaw is blunt (Figs. 5 and 6), the size overlaps (fore- 
wing length 8.0-9. 1 mm), and the nest (see below) is similar. But the 
shape of metasomal segment I and propodeal sculpture are 
different. Segment I is relatively narrower basally and more 
abruptly expanded posteriorly in pelor ( cf Figs. 1 and 2), and the 
propodeal carina is more reduced dorsally ( cf Figs. 2 and 3). The 
color is also distinctive. M. fraudulentus is lighter on the mesosoma, 
with more yellow on the sides of the thorax and propodeum, and the 
legs brown. The metasoma is black, at most tinged with yellow 
apically, on the three posterior segments in fraudulentus. It is brown 
and banded with yellow in pelor. 
These three species together with M. moralesi Zikan may form a 
monophyletic group, sharing the apomorphy of an emarginate cly- 
peus. Other species in Monogynoecus have the clypeus pointed or 
rounded (Richards, 1978). The emargination is broader in moralesi, 
which may be derived, and the other morphological features shared 
by pelor, fraudulentus and alienus appear primitive in the subge- 
nus, e.g. pronotal fovea present. But the nests of pelor and fraudu- 
lentus probably show derived similarity (see below), so these species 
may be sister-groups. They are generally quite similar, and further 
collecting may yet show that the differences represent geographical 
variation in one species. At present, they are best regarded as 
distinct species. 
