SUBFAMILY MESEMBRINELLINAE 63 
it incubates a single egg at one time, retaining the developing 
larva well into the second instar. .There is no chitinous vagina. 
The nulliparous uterus is very small and lies just ventrad of 
the rectum in the sixth and seventh segments. The developing 
larva within the uterus has the oral hooks near the anteroven- 
tral uterine wall and its posterior spiracles at the genital open- 
ing. The ducts of the spermathecae and accessory glands open 
into the center of a thickened membranous area on the antero- 
dorsal third of the uterus. This thickened area extends anterior- 
ly into the common oviduct, which divides into the lateral ovi- 
ducts, these beginning in the ovaries which are composed of only 
three or four ovarioles each. One ovariole usually develops dur- 
ing the period when a larva is developing within the uterus. The 
spermathecae are three in number, two on the right side and 
one on the left. These are in the form of long, sclerotized, tu- 
bular coils which are enclosed in thick tissue hoods. Their less 
sclerotized ducts are about as long as the accessory glands. The 
membranous accessory glands are two in number and are re- 
latively short. 
The ovarian egg is sometimes 2 mm. in length and 0.75 mm. in 
diameter. Only one egg develops at one time and it continues to 
grow while it moves from the ovaries through the ducts and 
hatches in the uterus. 
The fully developed first-instar larva occupies almost the en- 
tire posterior half of the abdominal cavity, the anterior half of 
which is filled with air-sacs. The common oviduct extends to 
the foremost portion of the uterus and the lateral oviducts then 
extend to the ovaries located posteriorly on the ventrolateral 
surfaces of the uterus. The spermathecae and accessory glands, 
portions of the digestive tract, rectum, and Malpighian tubules, 
' with numerous tracheal branches, are imbedded in fat body and 
tissue in the hindmost portion of the abdominal cavity. There 
is no evidence of placental development nor is there evidence of 
parental feeding, although Townsend (1934) stated, ‘‘The larva 
is apparently enveloped in a placenta trachealis.’’ Weber (1933, 
p. 5384) stated that the food of such larvae is supplied within the 
ego. I was unable to find secretory glands and it seems doubtful 
that sufficient food material is supplied by this means to yield 
larvae of the size produced by Huascaromusca bicolor (10-12 
mm.) or by H. facialis (12-14 mm.). 
The external and internal genital structures of male mesem- 
brinelline flies (Fig. IV) are similar in general appearance to 
those of the typical calliphorine flies. The ejaculatory bulb and 
its apodeme are proportionately larger than in Calliphora vomi- 
