27 
the appetite, the staring coat, the drooping head, the hanging ears, 
' the eyes at first injected and afterwards dull and expressionless,— 
all indicate an overwhelming malady. The animal trembles in all 
its members and staggers when it walks; its mucous membranes 
are at first congested, but later become pale except where points 
of inflammation mark the punctures of the pest. There is a high 
fever at first, with full and rapid pulse; but later this becomes 
feeble and threadlike, and sometimes intermittent, and death ap¬ 
pears after a few hours unless efficient treatment has been prompt¬ 
ly applied. 
Prevention and Protection 
Measures of prevention and protection against these insects are 
of two kinds,—the use of repellents intended to drive away the 
winged flies, and measures for the local destruction of the aquatic 
larvae. The repellents used are either smudges, or surface appli¬ 
cations made to keep the flies from biting. The black-fly will not 
endure a dense smoke, and the well-known mosquito smudge seems 
to be ordinarily sufficient for the protection of man. In the South, 
leather, cloth, and other materials which will make the densest and 
most stifling smoke, are often preserved for this use in spring. 
Smudges are built in pastures for the protection of stock, and are 
kept burning before the doors of barns and stables. As the black- 
flies do not readily enter a dark room, light is excluded from 
stables as much as possible during the gnat season. If teams must 
be used in the open field while the gnats are abroad, they may be 
protected against the attacks of the gnats by applying cotton-seed 
oil or axle-grease to the surface, especially to the less hairy parts 
of the animals, at least twice a day. A mixture of oil and tar, 
and, indeed, several other preventives, are in practical use in 
badly infested regions; but no definite test or exact comparison 
has been made with any of them in a way to give a record of the 
precise results. 
It is easy to drive the flies from houses or tents by burning 
pyrethrum powder inside; this either kills the flies or stupefies 
them so that they do not bite for some time thereafter. Lugger 
says that this method is in general use by the hunters and trappers 
of the Hudson Bay Company, and that he has also used it suc¬ 
cessfully in his numerous trips in Minnesota.* 
Oil of tar is commonly applied to the exposed parts of the body 
for the purpose of repelling the insects, and this preparation is 
supplied by the Hudson Bay Company to its employees. Minne- 
*Seconcl Ann. Rep. Ent. State Exper. Sta., E T niv. Minn., p 182. 
