HORSEFLIES OF THE SUBFAMILY TABANINAE 3 
transmission of disease. The irritation they produce in domestic 
animals results in loss of weight and milk production, runaways, and 
wounds due to kicking or hooking by animals trying to fight them 
off. These wounds often provide an entrance for bacterial or fly 
maggot infection. The loss of blood during an outbreak of horseflies 
has been computed by Webb and Wells (23) and may be very 
considerable. While man is not so seriously affected by tabanine 
species, their presence in large numbers at bathing beaches is often 
very annoying. 
The mechanical spread of anthrax by horseflies in the South is a 
well recognized example of disease transmission, and there is a strong 
possibility that horseflies play a considerable part in distributing the 
causative organisms of equine infectious anemia or swamp fever, 
equine encephalomyelitis or brain fever, and anaplasmosis of cattle. 
Their intermittent method of feeding greatly enhances the possibility 
of the mechanical transmission of diseases. In the Old World surra 
and other trypanasome diseases and blackleg are known to be trans- 
mitted by horseflies. In the United States tularaemia transmission by 
Chrysops has been demonstrated, and it is not impossible that some of 
the tabanine species may be vectors of the disease.* 
RELATIONSHIPS 
The family Tabanidae is characterized by having the apex of the 
wing included in cell R4, three-segmented antenna, the third seg- 
ment composed of annuli, the empodia pulvilliform, at least the mid- 
dle tibia with spurs, and the squamae large and conspicuous. 
In this paper the subfamily Tabaninae is treated in a broad sense 
to include all the species lacking spurs on the hind tibia. In addi- 
tion to the absence of spurs, ocelli are usually completely lacking 
and never more than rudimentary. As thus defined, the subfamily 
Tabaninae corresponds to the section Opistanoplae of Lutz, in con- 
tradistinction to the Opistacanthae, or Pangoniinae in the broad 
sense. Lutz (72) recognized three subfamilies in the Opistanoplae, 
the Tabaninae, Diachlorinae, and Lepiselaginae. Enderlein (3) in- 
creased the number of subfamilies in the family fronr the 5 of Lutz 
to 10, the Opistanoplae containing the Haematapotinae, Chasmiinae, 
Diachlorinae, Tabaninae, and Bellardiinae. The genus Lepiselaga 
and related genera he placed in the tribe Lepiselagini, subfamily 
Tabaninae, rather than retaining the subfamily Lepiselaginae of Lutz. 
Krober (77), in his catalog of neotropical Tabanidae, retained the 
subfamily Lepiselaginae and added the Stenotabaninae. 
In the Nearctic fauna we have representatives of three of the sub- 
families that might be recognized. These are the genus Haema- 
topota, the genus Diachlorus, and the genus Tabanus with its related 
genera. The writer does not feel that the genus Stenotabanus can 
be placed in a different subfamily from the genus 7’abanus, and if it 
were, certainly the genera Bolbodimyia and Whitneyomyia would 
require another subfamily rather than being placed with the genus 
Stenotabanus. The character of the closed cell R,, used to separate 
«For a further discussion of the economic importance of Tabanidae in North America, 
papers by Cameron (2), Knowlton and Rowe (7), Morris (14), Philip (46), Sanborn, Stiles, 
and Moe (18), Schwardt (19), Scott (20), and Webb and Wells (23) should be consulted. 
