The Sphegoidea of Nebraska 3 
C. Abdomen without a constriction between the first and sec- 
ond segments; second cubital cell receiving one or two 
recurrent nervures, or one or both recurrent nervures 
are interstitial with the transverse cubital nervures. 
D. Labrum free, well developed, subtriangular or semi- 
circular, wider than long; transverse median nerv- 
ire sitartely (sinuste. (22s cate yt. coe STIZIDAE 
DD. Labrum not free, entirely covered by the clypeus, or 
at most with only its apex visible; transverse me- 
dian nervure either straight or sinuate, 
NYSSONIDAE 
CC. Abdomen with a more or less distinct constriction between 
the first and second segments, the first segment coarc- 
tate; intermediate coxae contiguous; second cubital cell 
never receiving a recurrent nervure.... MELLINIDAE 
AA. Middle tibiae with only one apical spur (sometimes entirely absent). 
B. Front wings with two or three cubital cells; if with only one the 
head is transverse, not quadrate, and the eyes are deeply 
emarginate within; median cell in hind wings not twice as 
long as the submedian, the latter often longer. 
C. Abdomen with a strong constriction between the first and 
second segments; eyes often emarginate within. 
D. Front wings with two cubital cells, the second usually 
more or less indistinctly defined, sometimes en- 
tirely obliterated; abdomen elongate, clavate, the 
first segment petioliform and coarctate; eyes al- 
ways deeply emarginate within; head not wider 
than thorax, the temples flattened, 
TRY POXYLIDAE 
DD. Front wings always with three cubital cells, the second 
often petiolate, the second and third each receiv- 
ing a recurrent nervure; abdomen sessile or sub- 
sessile, sutures between segments usually deeply 
constricted; head wider than thorax, the temples 
rather broad; eyes generally normal, sometimes 
- } emarginate within ............ PHILANTHIDAE 
CC. Abdomen without a strong constriction between the first and 
second segments; eyes most frequently normal, rarely 
emarginate within. 
D. Abdomen sessile, never petiolate. 
E. Marginal cell usually appendiculate; transverse 
median nervure straight, not sinuate; mandi- 
bles more or less emarginate on their exterior 
margin; labrum small, usually completely hid- 
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