92 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 97 
tions, thus demonstrating the fallacy of making measurements by eye. 
In measuring the haustellum I have taken only its corneous portion ; 
the membranous parts sometimes extend its length slightly, but to 
measure them would mean the unnecessary addition of a variable 
element. 
This study has been made chiefly on the basis of material in the 
United States National Museum. Iam however, indebted also to the 
following individuals and institutions for the loan of small, though 
valuable, collections: Dr. H. J. Reinhard, Texas Agricultural Experi- 
ment Station; A. R. Brooks, Division of Entomology, Ottawa, On- 
tario; and Dr. C. H. Curran, American Museum of Natural History. 
As limited above, this complex of genera will trace with relative ease 
through Townsend’s? complicated keys to the families and tribes of 
Oestroidea. In the family key the genera * will run to couplet 47, page 
12; in the key to the tribes of Dexiidae, they run to couplet 4, page 27. 
The characters which, according to Townsend’s Manual, may be con- 
sidered diagnostic of the group under consideration, may, therefore, 
be summarized as follows: 
Head not swollen. Cheeks distinct, at least one-eighth eye length. 
Antennal arista thin, with short to medium pubescence. Epistoma of 
moderate width, slightly to moderately warped forward, distinctly 
shorter than clypeus. Proboscis once geniculated; corneous part of 
haustellum at least half head height, slender, often bowed or curved, 
set with scattered to rather dense, erect, short setulae. Frontal bristles 
moderately strong, at least one on each side placed below base of an- 
tenna; hind reclinate, frontoorbitals not closely approximated to the 
verticals; ocellars present though sometimes weak, proclinate, divari- 
cate. Prosternum ‘and propleura bare; tympanic ridge bare; thorax 
without plumose hairs. Pteropleural bristle shorter than the sterno- 
pleurals. Abdomen 4-segmented, ovate, not “wasplike”; tergites cov- 
ering ventral membrane and larger parts of sternites. 
In addition to the above, this group of genera may be characterized 
as follows: Form moderately slender. Head from lateral view trape- 
zoidal, its length at oral margin at least 0.8, sometimes equal to, that 
at base of antennae; front gently sloping, flat to moderately convex, 
its length equal to or slightly less than that of face; clypeus not or but 
slightly depressed, 1.25 to 1.50 as high as its maximum width, with- 
out a facial carina; parafacials bare, two to three times as wide at base 
of antennae as at narrowest point; vibrissae strong, each surrounded 
? Manual of myiology, pt. 3, 1936. 
° Proleskiomima, in which the prosternum is provided with hairs and bristles, is an excep- 
tion ; it will trace to couplet 33, page 10. 
*See footnote 8. 
