INTRODUCTION. 23 
are doubtless of very different nature in different species, or, as already 
hinted, of the same species under different conditions. This might be 
a sufficient repellant influence simply from the difference in odor, a 
difference we know to exist in different animals, or, for the species 
feeding upon the scales or excreted matter on the skin, a difference in 
the material making it unsuited to them for food. We must remember 
that the parasites have become adapted to certain species of animals 
through a long course of evolution and differ almost as much in their 
characteristics and necessities as the animals upon which they live. It 
may be worthy of note, in passing, that the most odorous of animals are 
comparatively free from parasites. Theskunk,' for example, has never 
been credited with harboring lice but in a single case, and this one 
(Goniodes mephitidis Pack.), once reported, if correctly referred to Goni- 
odes, has much of doubt in it, since all species of this genus are strictly 
bird parasites, and the specimen described may have been an accidental 
visitor on the skunk derived from some bird which had served it for 
food. 
To the practical stock breeder all these questions are simply subsid- 
iary to the one of how to contend with these various pests, and especially 
those which cause a serious loss, 
In general, it is most important for him to know to what ex.ent a 
certain insect is capable of doing injury, the time and mode of its 
attack, the animals it may affect, and the best methods to adopt for the 
prevention or check of the injury. 
While in some of the insects to be discussed here the different stages 
of their existence appear to have little to reveal concerning the methods 
of treatment, there are others which we can hope to deal with only 
from a thorough knowledge of all steps in their development as a foun- 
dation. We hope the reader who has any desire to make use of such 
knowledge will bave patience with those parts which may seem to him 
unnecessary details, remembering that it is often in some minor detail 
of existence, apparently of slightest importance, that we find the clew 
to successful warfare with a serious pest. 
Much annoyance may be saved in some cases by a knowledge of the 
animals to which certain species of parasites are confined, both by pre- 
venting infection among those to which a certain parasite is common, 
and by avoiding the trouble of unnecessary restrictions in case the para- 
site can not occur on two or more animals which it is convenient to 
allow a common pasture, corral, or stable. The list of parasites arranged 
according to host animals, Chapter VIII, which has been prepared with 
care from all accessible records concerning such species, will form a 
ready means of determining such questions without having to spend 
time in reading through the body of the work to find it. 
The subject of remedies and preventive measures is treated fully 
'We include elsewhere description of a louse, Trichodectes mephitidis, that has been 
found in abundance on the skunk. 
