66 THE BLOWFLIES oF NortH AMERICA 
This genus differs from other genera in the subfamily by lack- 
ing posthumeral and preacrostichal bristles. It differs from — 
Huascaromusca in head proportion as well. 
Promesembrinella semiflava (Aldrich), new combination 
Mesembrinella senuflava Aldrich, U.S. Natl. Mus., Proc. 66(18) : 
14-15, 1925. (Type, male from La Suiza de Turrialba, Costa 
Rica, No. 26799, U. S. National Museum.) 
A yellowish to brown species with faintly infuseated wing, 
front, antenna, palpus, and legs orange, the dorsum of thorax 
and the third and fourth abdominal segments metallic blue. 
Male. Head width at greatest 14.0; length at antenna 6.2 and 
at vibrissa 5.2; eye height 11.0; head height 12.0; elypeus with 
length fully twice width, orange, rather silvery pollinose; epis- 
toma but very slightly warped forward from clypeal plane; 
bueea 0.10 of eye height, orange, golden pollinose, with a few 
scattered black hairs, some pale hairs before the metacephalic 
suture; frontale totally obliterated at narrowest portion of front, 
orange anteriorly; frons at narrowest (about two units below the 
foremost ocellus) 0.03 of head width, 0.10 at vertex, and 0.20 
at lunule, orange in ground color anteriorly, dark brown to 
black posteriorly, golden pollinose, without fine hair outside 
frontal rows of bristles; vertex dark brown to black, brown 
pollinose; frontal row of bristles vestigial posteriorly, fading out 
at narrowest portion of front and composed of about five 
bristles, only the anterior ones strong; parafaciale golden pol- 
linose over orange ground color, 1.2 in width opposite lunule, 
narrowing to about 0.6 below; faciale low, rounded, broad, with 
only a few small black setae above the vibrissae; vibrissae at 
oral margin, set 3.6 apart; antenna orange, third segment three 
times as long as second and reaching almost to the vibrissae; 
arista orange brown, darker apically, the ciliation dark brown; 
palpus orange, 3.5 in length; back of head dark brown to black 
above; metacephalon orange, the former silvery pollinose, with 
one row of postocular cilia and with orange colored hair. 
Thorax orange, dorsum dark brown to bluish black metallic, 
with some white pollen which is particularly noticeable anter- 
iorly, and with two dorsal, longitudinal, shining black stripes 
outside the dorsocentral rows of bristles which extend posteriorly 
to the seutellar suture, and with less distinct and narrower 
stripes outside the acrostichal rows of bristles, which do not 
extend beyond the suture; pleura slightly silvery, with orange 
hair; propleuron slightly silvery, with fine orange hair; pro- 
pleural bristles two; sternopleural bristles two, both strong; 
