ART. 11. GENUS MESEMBRINELLA GIGLIO-TOS——-ALDRICH, 9 
Generic characters: hypopleural bristles present, arista plumose to 
tip, eyes bare, bend of fourth vein obtuse and broadly rounded, 
thence straight and ending only a little before the apex of wing (if 
there is any concavity at all it is just at the tip, not immediately 
after the bend); first posterior cell wide and broadly open, sometimes 
very broadly; frontal bristles not continuing below insertion of 
antennae; female with a pair of decussate bristles on the frontal 
stripe, below the ocelli; eyes bare; bucca narrow, about one-fifth to 
one-sixth eye height; first and second abdominal segments without 
median marginals; no discals except in two species on the fourth 
segment. They are easily separated from Calliphora by the course 
of the fourth vein, the much narrower bucca, the arista plumose to 
the tip, hind calypter bare above, and in the female decussate bristles 
on the front. 
The two species herein identified as Mesembrinella bicolor Fabricius 
and bellardiana, new species, are fairly common in collections (I have 
examined approximately 50 of the former, 12 of the latter), but it is 
a very difficult matter to get enough of the others to determine the 
value of the characters. Both of the common species vary in ‘the 
number of sternopleurals; posterior acrostichals may apparently vary 
from one to three pairs; a third humeral is usually present, but often 
small and sometimes merely hairlike; the foremost anterior dorso- 
central also may be small, so there is no real difference worth men- 
tioning between two and three in this series; supraalars seem to vary 
from two to four in the same species; there may be two lateral scu- 
tellars or only one. On the other hand, there seems to be more 
constancy in the color of the wings than would be expected; the 
second presutural is regularly present in some species, absent in 
others; while one or two pairs of anterior acrostichals as compared 
with none seems to be a stable character. Color of the legs, as in 
brunnipes, I view with misgiving, but have too little material to 
prove anything. 
The presence or absence of the second presutural bristle separates 
two very natural groups, the former including the type species; the 
absence of this bristle is generally accompanied by the absence of 
the second posthumeral, but the latter is well developed in cruciata 
and almost as well in facialis. The second presutural when present 
is mesad of the large outer presutural, which is always present, and 
a little behind the middle of a line drawn from the outer one to the 
dorsocentral, which is just before the suture. The posthumeral, 
which, as stated, usually varies with this, occurs halfway between the 
outer presutural and the humeral swelling. 
60466—23—Proc.N.M.vol.62 31 
