THE CATTLE GRUBS OR OX WARBLES 107 
ment than would be supposed. On an average it required an hour 
to treat about 98 grubs by, the apphcation of oitments, such as 
iodoform-petrolatum to cysts in the backs of cattle. Undoubtedly 
this work could be done much more rapidly in herds showing a 
fairly heavy infestation. 
The cost of materials and equipment should be considered, espe- 
cially if large herds are to be treated. The fact that no instru- 
ments or materials are needed for the ordinary hand extraction 
commends that method. With the use of omtments, powders, and 
washes practically no equipment is required. The cost of forceps 
or scissors for the puncturing and pulling method of extraction is 
not great, but this method requires rather more care and a higher 
degree of training for the work than is necessary for using’ the 
oil-ean injection method or for applying washes and powders. 
The cost of the chemicals used varies considerably with the ma- 
terial, and there is also considerable difference between the whole- 
sale and retail prices of each. Iodoform-petrolatum ointment costs 
about 814, cents per ounce at the usual wholesale price. The retail 
price is about 15 cents per ounce. An ounce will treat between 
125 and 200 grubs, thus making the retail cost of the ointment about 
12 cents per 100 grubs. Pyrethrum ointment is much cheaper, 
as it costs about 5 cents per 100 grubs. The only objection to this 
ointment is that the pyrethrum powder must be fresh to be potent. 
With such materials as carbon tetrachloride and benzol, it was 
found that a pound of either would treat about 500 warbles. Since 
these materials are comparatively inexpensive the cost is extremely 
low. 
As yet derris is not available on the open market in this country, 
but it is probable that it will retail at approximately $1 per pound. 
Tobacco dusts of all grades are very much cheaper, but they do 
not appear to be equally effective in any strength, and furthermore 
their strength as well as mechanical make-up varies considerably. 
It is probable that if further tests prove that very fine tobacco dust 
with a fairly high percentage of nicotine is as effective as the writers’ 
preliminary experiments indicate, this material may be standard- 
ized for this purpose. 
CONTROL THROUGH INDIVIDUAL EFFORT 
The results of control measures applied by an individual cattle 
owner when he is more or less closely surrounded by livestock are 
likely to be disappointing. Three tests have been made by the writers 
in which the grubs have been destroyed rather systematically for 
periods of from two to four years. It is true that all grubs were not 
destroyed each year, but the work was probably done as thoroughly 
as it would have been if left to the cattle owners. The pastures where 
the treated cattle ranged were in close proximity to others in which 
untreated stock were kept. In none of these tests was a striking 
reduction observed in the number of grubs during the year following. 
The most thorough work along this line was done on the dairy 
and breeding farm of J. T. Orr, near Dallas, Tex. From 45 to 100 
head of cattle were carried on this place. During the grub season 
of 1920-21 the cattle were examined and grubs destroyed only once, 
on January 29. The average number of grubs per head then was 
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