HORSEFLIES OF THE SUBFAMILY TABANINAE 5 
tubercle. The writer retains the former term, since the tubercle does 
not bear ocelli in the Tabaninae. On the "frons are usually two 
denuded calli, one at the lower margin, formerly called the frontal 
callus, but which the writer terms the basal callus, and the median 
callus, usually narrower and often broadly joined to the basal callus. 
The clypeus lies below the antennae and above the oral margin, with 
the genae to each side. The antenna consists of three segments, the 
third composed of a large basal portion and an attenuated annulate 
portion. The number of divisions in the third antennal segment is 
frequently of generic significance, the basal portion being the first 
division. The basal portion is compressed and usually has a dorsal 
angle near its base; by the width of the basal portion is meant 
its greatest vertical ‘dimension. 
THORACIC CHARACTERS 
The term prescutal lobe is used in place of antealar callus. The 
Comstock-Needham terminology of the wing veins and cells is used 
because it is easily apphed in the Tabanidae and because this ter- 
minology 1s being used increasingly both in this country and abroad. 
While it will probably be necessary to change the original designa- 
tion of the veins in the tabanid wing more accurately to reflect the 
morphology, the proper terminology is still so doubtful that, for 
descriptive purposes, the writer retains the old terminology. By 
furcation is meant the point of separation of veins R, and R;, and 
by normal venation is meant that of the typical 7abanus wing with 
no stump vein from base of vein R,; and with cell R; open. For de- 
scriptive purposes the writer uses the term cross veins to include all 
of the shorter, relatively transverse veins, some of which are only 
basal portions of longitudinal veins, but which are all subject to 
marginal infuscation. 
SEXUAL DIMORPHISM 
This is found principally in the head structures. The eyes of the 
male are holoptic and they frequently consist of two types of om- 
matidia, the upper ones large and the lower ones small, with the 
color pattern confined to the lower ones. The antenna is decidedly 
more slender in the male. The maxillary palpus of the male is 
reduced, the second segment being short and extending forward, 
rather than longer and curved downward. The hair of the head and 
thorax is usually darker in the male. The abdomen of the male is 
narrower apically than that of the female. The writer has tried 
to find characters in both the male and female terminalia but has 
succeeded in finding none of any value. In this publication he de- 
scribes the males very briefly, both because they are much less fre- 
quently encountered and because, save for the secondary sexual dif- 
ferences, they usually very closely resemble the female. 
ILLUSTRATIONS 
The illustrations used are semidiagrammatic in that no attempt 
is made to indicate the color patterns of the head or antenna, the 
calli of the frons are made black regardless of the actual color, and, 
except on the antenna, the hair is not shown. Accuracy of propor- 
