OT ee ve “ 
‘Negation WOR PB St 
INTRODUCTION. | “21 
the losses they occasion until some of the animals are so seriously 
affected as to lose flesh or be threatened with death. In the meantime 
the loss must have been very great, since all of the animals must have 
been fed sufficiently to provide for the parasites, and also to keep up 
the increased vitality of the animal to meet the demands made by the 
presence of an irritating agent. 
For actual statistics we must confine ourselves to instances where 
the presence of the parasites has resulted in the actual death of 
numbers of animals, or to a recognizable loss or depreciation on the 
animals or some product from them. These must naturally fail to pre- 
sent the whole truth, since isolated cases of the same kind will gen- 
erally fail to be recorded. 
Murray cites Delafond and Bourgignon as authority for the state- 
ment that in the valley of Prattigau, in the Grisons, Switzerland, in 
the years 1851, 1852, and 1853, out of upward of 2,500 goats, the half 
were attacked and 500 died from effects of the parasitic mite, Symbiotes 
bovis. . 
Reference to the sections on buffalo-gnats and bot-flies will show 
some instances where more or less definite figures can be cited as to the 
losses to stock industries from the attacks of injurious insects. It will 
suffice to mention here that the loss in a single county of Tennessee 
from buffalo-gnats in the one year 1874 was estimated at $500,000, and 
similar losses have occurred in many different years and over large 
tracts of the lower Mississippi Valley. Or we may cite the estimated 
loss in the United States due to one single species of bot-fly, $50,000,000, 
a species, moreover, which could be exterminated more certainly and 
quickly than any other with which we are acquainted. 
POPULAR NOTIONS ABOUT PARASITES. 
There are certain widespread uotions regarding the presence of par- 
asites or vermin on stock, and it, may be in place to call attention to 
one er two of them here. 
One of these is that only poor or weak animals are infested, and that 
of animals otherwise similar they will attack lean rather than fat ones. 
It may be quite frequently the case that animals noticed as “lousy” 
are the weak ones of the herd, but it should be remembered that the 
lice seldom attract attention until they become so numerous that their 
effects on the animal may be the real cause of its poor condition. It 
can not, certainly, be the case that they select only the weak and lean, 
for we have found lice in very fair numbers on animals in apparently as 
good condition as any others in the herd, including those upon which 
no lice at all could be found. It is true that certain animals in the 
herd may remain entirely free from lice, even when others in the same 
herd are badly infested, but that this is due purely to their being fat 
or in excellent health seems open to much doubt. 
Another idea is that white cattle are infested rather than dark 
ones, an idea which we have heard most emphatically urged by many 
