260 
NORTH AMERICAN MYRMOSIDAE 
Second ventral segment near its base with a well-defined undulating trans- 
A^erse ridge; j)ygidium with its lateral margins poorly defined, the median 
area very indefinitely raised; lower margin of each antennal socket 
armed with a tubercle projecting ventrad; squama obtuse; apical 
portion of uncus bent backwards and notched at apex (figures 21 and 22). 
crassa new species 
8. Propodeum with a strong transverse carina separating the dorsal from the 
caudal surface (9) 
Propodeum without a transverse carina (12) 
9. Distance from the apex of the cell 2d Ri -)- Ro to the apex of the stigma .7 
the length of the stigma or more (figure 11) (10) 
Distance from the apex of the cell 2d Ri -\- R2 to the apex of the stigma .3 
the length of the stigma (figure 5); greatest dorso-ventral thickness of 
the petiole .4 of its length; second ventral segment simple. 
carinata Fox 
10. Petiole Avith a long slender anterior neck, but little swollen tOAAmrd the 
apex, its length three times its greatest dorso-ventral thickness; second 
ventral segment with a mere trace of a longitudinal carina at its base. 
idiotes Cockerell 
First abdominal segment short, thick, not anteriorly produced into a neck, 
half as long again as its greatest dorso-A^entral thickness; second A^entral 
segment Avdth a sharp longitudinal carina at its base (11) 
11. Clypeus CA'enly rounded, the margin eleA^ated; mesopleura each Avith a 
poorly marked rugosity, but not as in the folloAving species; the distance 
from the end of the stigma to the apex of the marginal cell .8 the length 
of the stigma aequalis Fox 
Clypeus AA'ith its median portion produced and truncate, not elcA’ated; 
mesopleura each with a large impressed basin, surrounded by rugae and 
posteriorly by a carina; the distance from the end of the stigma to the 
apex of the marginal cell equal to the length of the stigma (figure 11). 
noctivaga new species 
12. Cell R5 minute and far remote from the base of the cell 2d R1-I-R2; the A'ein 
R4 but slightly apicad of the radial cross-vein, far basad of the apex of 
the cell 2d Ri-|-R2. Small species, 6 to 8 mm. in length; middle of 
clypeus with a tubercle (except possibly in gaudii) (13) 
Cell Rs larger, triangular and reaching to or nearly to the base of 2d Ri 
R2; the A^ein R4 far apicad of the radial cross- A^ein (16) 
13. Propodeum rugose or smooth, not lineolate; color never black (14) 
Propodeum transA'ersely minutely lineolate. Color black. 
gaudii Cockerell 
14. Propodeum Avithout sculpture, other than a median basal grooA’e, its 
lateral angles rounded ; thorax honey yellow, head and abdomen darker. 
Length, 6 mm. (New Mexico) (15) 
Propodeum Avith the sides of the dorsal surface and the postero-lateral 
angles rugose; mandible with three teeth, a strong carina reaching the 
inner tooth; rather uniformly dark castaneous. Length, 8 mm. (LoAver 
California) petlolata Fox 
