130 Tae BLowFuiEs of NortH AMERICA 
Female. (Color plate I). Head (pl. 2, C) length at antenna 
7.1 and at vibrissa 7.6; width 15.9; height 13.5; eye height 9.5; 
bueca 0.36 of eye height; front at vertex 0.27 of head width, 
0.38 at lunule; frontale with nearly parallel margins, slightly 
widening toward lunule and narrowing toward ocellar triangle, 
with several scattered interfrontal setulae which are not paired 
or consistently placed, bright reddish orange anteriorly, red 
orange to brownish from vertex to occiput; normally without 
proclinate frontoorbital bristles; third segment of antenna 3.7 
times as long as second. Abdomen colored as in male and dif- 
fering most obviously from that of macellaria in lacking bright 
silvery-pollinose spots laterodorsally on the fourth segment. 
Otherwise similar to male except for normal sexual differences. 
Length. 8-10 mm. 
The coloration of this species depends somewhat upon ecologi- 
eal conditions. Tropical specimens are often noticeably smaller, 
more brilliantly orange yellow and metallic bluish, with legs 
tending toward deep brown, and wings more deeply brownish. 
Specimens from the United States, especially from the Middle 
West, are definitely more metallic bluish black and the legs 
are shining greenish black. The usual variations in the color of 
- such specimens are in the basicostal seale, the occiput, the sub- 
costal sclerite, and the legs. Investigations by Melvin in Texas 
indicate that the intensity of the color of these parts may be 
determined by temperature. Under normal conditions in na- 
ture a large majority of specimens of this species can be sep- 
arated from macellaria by the color of the legs, basicostal scale, 
and occiput. There are, however, so many constant characters 
by which to differentiate the species that it should not be neces- 
sary to refer to those which are known to be variable. 
Distribution. Nearetic and Neotropical: United States south- 
ward to southern Brazil and northern Chile. 
This semitropical species occurs throughout the southern part 
of North America. Its range sometimes extends northward to 
central California in the West and to northern Iowa and Indiana 
in the East. It has not been collected northeast of South Carolina. 
It occurs in south Florida and south Texas during the entire year. 
Specimens of americana are often found in collections identi- 
fied as Paralucilia fulvipes (Macquart) or Chrysomyia wheeleri 
Hough. Small specimens may sometimes be found under the 
name Cochliomyia macellaria (Fabricius). The specimens dis- 
cussed as Compsomyia macellaria (F.) by Townsend (1895, p. 
619) and later determined as Compsomyiops fulvipes (Maeq.) by 
Aldrich, are americana. 
