163 
In discussing this paper Mr. Atkinson remarked that, while there 
were characters present in the species he had described that seemed 
to place it in the genus Tylenchus, he had been of the opinion from the 
first that his species was introduced into the United States, and would 
not be surprised if it should prove, on more careful examination and 
comparison with the one described in the paper just read, to be identi- 
cal with the latter. 
The following paper was then read : 
METHODS OF ATTACKING PARASITES OF DOMESTIC ANIMALS. 
By Herbert Osborn, Ames, Iowa. 
In dealing with insect parasites of domestic animals we need to con- 
sider, first, the method of attack of these parasites, and Ave may con- 
veniently separate them into the external parasites and the internal 
parasites. Among the former we have various species of lice, itch- 
mites, ticks, and can also include those forms which affect the external 
parts of the body by depositing eggs in sores. In the latter series we 
may include the different kinds of bot flies affecting the internal organs 
and certain forms of degraded Acarina which also affect certain inter- 
nal organs. It is unnecessary here to detail the mode of attack of the 
external forms more than to mention that some pierce the skin to suck 
the blood, others simply feed upon external excretions of waste mate- 
rial, while others may burrow beneath the epidermis, producing pus- 
tules, scabs, etc. 
First among the methods of treatment we should consider that of 
prevention, since, for perhaps the majority of the parasitic forms, a 
little effort in the direction of prevention is far more effective than 
costly and laborious methods later on. 
With a large majority of parasitic species, including all of the lice, 
the sheep-infesting Hippoboscidse and all of the Sarcoptidse, infection 
results from the mingling of parasitized animals with those which are 
free from parasites. It is therefore possible by attention to ani- 
mals introduced into a herd, or sometimes into a new section of 
country, to prevent entirely the introduction of the parasites. To 
accomplish this it is necessary to examine introduced animals, and if 
infested, or suspected of being infested, use thorough treatment upon 
these. In the case of introduced cattle infested with Hypoderma it 
would seem possible that they might, by being carefully watched and 
the grubs destroyed, be prevented from introducing this pest in any 
new locality. Since the parasite occurs only in the bodies of cattle 
during the winter season, I see no reason why attention to imported 
cattle should not serve to totally exclude this pest from any locality 
which has hitherto been free from it. The bots in horses may be pre- 
