8 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE, 1010 
An extensive experiment with toxaphene was undertaken in cooper- 
ation with the Hercules Powder Co. Hereford steers 6 to 9 months 
old were Bprayed with 0.5-percent toxaphene emulsion, some at inter- 
vals of 2 week- and others of 1 month. Six groups of 2 or 3 annuals 
received from l to LO treatments and 6 animal- received 12 treat- 
ments. Fat -ample- were taken by biopsy from each group before and 
after treatment, and analyzed tor organic chloride. The results 
showed little evidence of accumulation of toxaphene in the fat. The 
technique of taking fat -ample- at intervals From the experimental ani- 
mal- has greatly advanced progress in investigations od the toxicity 
of insect icides to livestock. 
New Insecticides Tested Against Livestock Pestfl 
Experiments with the new insecticides for the control of livestock 
were cont inued. 
For the control of horn Hie- on cattle, methoxychlor, TDE, and toxa- 
phene were about equally effective. Spray- containing 0.5 percent 
of any of these insect icides provided good control for 3 to 1 weeks. A 
spray containing 0.1 percent of pyrethrins plus 1 percent ofpiperonyl 
butoxide was effective for about 1 week-. DDT is -till recommended 
for the control of horn flies on beef animals. Tl >E and methoxychlor 
are al-o recommended for this purpose. 
In tests against stable flies, metnoxychlor was found to be superior 
to DI )T when applied to screen cages as a residual t reatment, especially 
when the cages were c\po-ed to sunlight. When applied to animals 
both methoxychlor and pyret hrnni-piperonyl butoxide either repelled 
the flies <>r killed most of those that fed during the first 3 days after 
the t reatment. 
Satisfactory control of the Gulf coast tick on cattle was obtained 
with toxaphene and also with a combination of DDT and benzene hexa- 
chloride when the animals were treated every 2 to •*> weeks. DDT alone 
was not effective against engorged ticks. Dips or sprays containing 
0.5 percent of toxaphene or 0.5 percent of 1 >I >T pins sufficient benzene 
hexachloride to give 0.025 percent of gamma were used. Chlordane 
was also promising for t he cont rol of t icks affect 'hilt livestock. Meth- 
oxychlor was in general less effect ive than the other chlorinated hydro- 
carbons tested. 
Against the sheep tick benzene hexachloride, chlordane, and toxa- 
phene continued to be Superior to other chlorinated hydroearhons. 
Dips gave better com rol than sprays. A single dipping with inn-tain 
■ave complete control. However. SpraVS containing 
0.5 percent of chlordane or technical benzene hexachloride (0.05 per- 
cent of gamma isomer) generally gave excellent pract ical i ont rol wnen 
applied in proper amounts with suitable equipment, especially on sheep 
recent ly shorn or wit h short fleece. 
T( ts in L948 confirmed previous reports that none of the chlori- 
nated hydrocarbon insecticides were effective for the control of cattle 
grub larvae in the backs of animal-. Treatments with all the com- 
mercially a\ a i la Me insect icides of this type at 2-week intervals during 
the egg-layii on failed to prevent cattle grub infestations. 
