2 MISC. PUBLICATION 305, U. 8. DEPT. OF AGRICULTURE 
the western part of the United States and Canada. Since Osten 
Sacken’s time many species have been described by Bigot, Marten, 
Whitney, Hine, McDunnough, Philip, and others, and a number of 
the species of older authors have been recognized and others synon- 
ymized. The need for gathering this information together, for more 
accurate descriptions of the known species, for recognition of new 
ones, and for serviceable keys that more correctly define the genera 
and species of this economically important group of insects has 
become imperative; the purpose of this publication is to satisfy these 
demands. 
In this publication 11 genera and 154 species of Nearctic * Tabaninae 
are recognized. Fourteen species and 1 variety are described as 
new, 1 genus has been transferred to the subfamily Pangoniinae, 1 
subgenus has been raised to generic rank, 20 species and 1 variety 
have been sunk as synonyms, and 3 species have been reduced to 
subspecific or varietal status. 
No claim can be made for this publication as a definitive work on 
the subject. Judging from the number of new species that have been 
found within the past few years by Philip and the writer it is quite 
probable that others remain to be discovered. Further study of types 
now in European museums will probably necessitate changes of names 
in certain cases. It is possible that further division will be neces- 
sary in certain species, notably Atylotus insuetus, Tabanus lineola, 
T. sulcifrons, and 7’. septentrionalis. 'These species occur in consid- 
erable abundance at times and show variations which may be of 
subspecific or even specific value. With the material at hand, how- 
ever, the writer has been unable to delimit the variants satisfac- 
torily. Finally, the genus 7’abanus, as restricted in this publication, 
still contains species of considerable divergence and it may be that 
satisfactory characters, usable in keys, can still be found to subdivide 
the genus further. Many characters have been suggested in the past 
and there is no lack of available names, but none of the characters 
proposed appears to hold satisfactorily. 
ECONOMIC IMPORTANCE 
As irritating pests of domestic animals and proved or suspected 
transmitters of disease, the Tabanidae probably rank next to the mos- 
quitoes in importance. Within the subfamily Tabaninae the serious 
pests are almost all confined to the genus 7abanus. Haematopota 
americana will attack man and animals readily but rarely occurs in 
numbers sufficient to cause serious annoyance, and although Diachlorus 
ferrugatus, the yellow fly of the Dismal Swamp, is troublesome 
in the coastal swamps of the southeastern part of the United States, 
its range is limited and sparsely inhabited. A number of species of 
Tabanus, however, occur in large enough numbers to make them seri- 
ous pests. Notable among these are 7’. nigrovittatus of the Atlantic 
and Gulf coasts, sulezfrons of the East Central States, and punctifer, 
septentrionalis, sonomensis, and rhombicus of the West. 
The damage done by the horseflies is due both to the annoyance and 
loss of blood caused by the feeding of the females, and also to their 
3 As considered in this publication, the Nearctic region comprises all of North America 
north of Mexico. : 
