256 
NORTH AMERICAN MYRMOSIDAE 
posterior border. The middle coxae are each covered at base 
with a scale-like projection of the mesosternum, and there is a 
similar, thicker projection of the metasternum at the base of each 
posterior coxa, differing slightly in form in different species. The 
propodeimi usually has definite dorsal, caudal and lateral faces, 
the two former separated in some groups of species by a strong 
transverse carina, an important specific character. In rare cases 
the propodeum is very low, entirely rounded, and without definite 
faces; sometimes the hind angles are prominent and punctured 
or rugose, but are usually rounded and only slightly roughened. 
The dorsal face is generally polished, without sculpture, or with 
a median channel; the posterior face is roughened by the insertion 
of numerous erect hairs, as are also the upper parts of the sides. 
The dorsal face is usually strongly declivous. 
The wings present important specific characters. They all 
agree in having the venation terminate not more than two-thirds 
of the wa\^ from base to apex, the rest being free membrane 
(figures 5 to 20). The length of the stigma, and the length and 
shape of the marginal cell (2clRi-|-R2) are variable among the 
different species, in fact the former has been made a chief charac- 
ter for distinguishing Andre’s genus Milhita from Brachycistis 
(compare figures 20, 12, 8 and 11). The cell R4 is in rare cases 
not enclosed (figures 9 and 20). Its height as compared with its 
length must be used specifically with caution, as it is somewhat 
variable. The cell R5 is usually short and triangular, but in a 
large group of species elongate, by reason of the radio-medial 
cross-vein (r-m) being inserted on media (M) close to the medio- 
cubital cross-vein (ni-cu), (compare figures 5, 19 and 20, with 6 to 
10). In one or two species in this group the position of r-m, 
while always close to m-cu, varies from apicad to basad thereof, 
while in others it is more stable. In a few species the radial 
cross-vein is apicad of R5, and therefore the cell R5 is “petiolate” 
and very small (figures 19 and 20). Other features of the wings 
will be apparent from the illustrations. 
The armament of the legs is of importance for specific differen- 
tiation. The tibiae and tarsi are closely pubescent. In some 
sjiecies the anterior metatarsi are armed with a row of three or 
four spines on the posterior border and two on the inner surface. 
