SUBFAMILY MESEMBRINELLINAE 
The flies which belong to this subfamily differ considerably 
from typical Calliphoridae. They are mostly testaceous with 
metallic-colored abdomens, and are the largest of the North 
American calliphorid flies. 
Little is known concerning the biology of any of the species 
which belong here. Both males and females are more or less 
erepuscular and are never found in bright sunlight. During 
periods of bright sunlight adults retreat into the darkest por- 
tions of the jungle. In early morning and late afternoon, or 
when the sun is concealed by clouds, they may be collected in 
open areas in the forest. Both sexes may be collected commonly 
on decaying fruits, feces of birds and animals, juices of vegeta- 
tion, fermenting substances, and other decaying substances. 
They rarely fly more than a few feet above the jungle floor. Males 
often congregate on low foliage near sources of attractive food. 
Females may be collected either on foods or as they fly slowly 
through the shadowed jungle. The adults of these species are 
among the most abundant of all flies in American tropical rain 
forests and in behavior they are unlike any of the other ealli- 
phorine flies I have ever collected. 
All specimens belonging to the subfamily Mesembrinellinae 
possess the following characters in common. 
MALE AND FEMALE. Head wider than high, length at an- 
tenna and at vibrissa half or less greatest width; length at oral 
margin and at vibrissa nearly equal; epistoma gently warped for- 
ward from clypeal plane and nearly or quite as wide as clypeus; 
metacephalon not apparent and the lower posterior margin of 
head rounded in profile; bucca comparatively narrow when com: 
pared with eye height; eye large, elongate-oval, set nearly 
straight in head, bare; inner vertical bristles strong, decussate; 
postvertical bristles weak, proclinate; interfrontal bristles pres- 
ent in female, absent in male; ocellar bristles large, proclinate; 
postocellar bristles weak, proclinate; clypeus sunken, shallow; 
_ facial carina absent or not apparent; parafaciale bare; faciale 
slightly coneave in profile, the edge rounded, low; vibrissa slight- 
ly above oral margin, with a second elongate bristle slightly 
below this, and often with a third and a fourth bristle at or near 
juncture of the lower anterior margin of head with the lower 
margin of the epistoma; proboscis about two-thirds head height; 
haustellum nearly five-eighths length of proboscis, stout, sparse- 
ly setose; palpus clavate, thickened apically; antennal base at 
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