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solvent is about the minimum advisable dilution for external treatment; 
the external' treatment is -fully as efficient as the injection; and the 
inclusion of the other derris resins, in addition to the rotenone, 
does not add significantly to the efficiency of the preparation. As 
^ould "be expected, more of the solution was used in the external appli- 
cation than was required 'for injection. Approximately 400 cc. of the 
solution was used in treating externally the .backs of 14 cattle carry- 
ing a total of 317 grubs. 
Wells ( 311 ) in 1940 published directions for the use of derris and 
cube washes in the control of cattle grubs. The powder, soap, and 
water are mixed in the following proportions: Water, 1 gallon; cube 
or derris powder (5 percent rotenone), 12 ounces; soap, 2 ounces. One 
gallon of the wash is sufficient to treat the backs of 12 to 16 adult 
cattle, depending on ho™ long and how thick the hair is. 
Wells and Schroeder ( 313 ) in 1939 reported on the effectiveness 
of derris washes on cattle grubs. Washes consisting of 8 and 12 
ounces of derris per gallon of water, plus 4 ounces of soap, apolied 
at the rate of l/3 quart tier animal, are less toxic to Hypoderma bovis 
than to H. lineatum . In the formrr species the third instars were 
more resistant to the meshes than "ere the second instars '"hale with 
the latter species the reverse was true. Hand rubbing of the backs 
of the animals after amplication of the insecticide ^ras more effective 
in killing H. lineatum larvae than was brush rubbing, but in treating 
animals infested with H_- bovis the latter method was just as effective 
as the former. . • 
The United. States Department of Agriculture, Bureau of Animal 
Industry ( 281 ) in 1940 stated the t experimental work was continued with 
washes containing derris powder and cube powder to determine their 
value and relative effectiveness as larvicides for 'the common species 
of ox warbles ( Hynoderna lineatum ) . The washes ^ere -prepared just before 
application end consisted of ^arm water, soap, and derris or cube powder, 
1 he soap, usually in flake form, was added to the warn --ater in the 
proportion of 4 ounces to a gallon, and the derris or cube powder in 12 
or 16 ounces per gallon. About 1 pint of wash was ap-nlied along the 
back of each animal treated. The liouid ^s then spread evenly over 
the back and sides and into the hair coat with an ordinary scrub brush. 
The experimental cattle "ere located in Texas, New Mexico, Colorado, 
and Missouri. They - r ere infested with grubs of H. lineatum . Grubs of 
H. bovis Deg. ^ere not found in anv of the cattle. The cattle were 
treated when grub openings began to a-npear in their skins. Derris and 
cube ponders "ere eaually effective as larvicides for settle grubs. 
The powders containing 4 percent of rotenone, used in the proportion of 
12 ounces to a gallon, were as effective in killing grubs in situ as 
those containing 5 percent, "'hen used in the proportion of 16 ounces to 
a gallon, but the former was not so effective as the latter in killing 
grubs that ce ^e up after treatment was applied. In most cases more than 
one treatment m es necessary to eradicate the grubs. Some treatments 
