﻿88 BULLETIN 136&, U. S. DEPAETMENT OF AGRICULTURE 



ing the eggs or young larvae as they hatch, by applying insecticides 

 to those portions. One of the most convenient and effective methods 

 of accomplishing this is through the utilization of shallow vats. 

 In 1918 experiments were begun to determine the effect on the 

 infestation of dairy cattle of the use of standard arsenical solution. 

 One-half of the cows in a dairy herd was allowed to pass through 

 a wadnig vat containing the solution about 1 foot deep, at invervals 

 of four days. The other half of the herd was not treated, being 

 kept as a check. In the first year's test 16 cows were treated and 

 the following season these were found to be infested to almost iden- 

 tically the same degree as the 16 cows which were not treated. In 

 1919 the same herd was utilized in a test under similar conditions, 

 a standard sodium arsenite solution containing about 19 per cent 

 arsenic trioxide being used in the vat. The following season the 

 dipped cows had an average infestation of 7.18 grubs per animal 

 and the untreated cows showed an average of 5.65 grubs per animal. 

 During the spring of 1920 the same herd was again utilized in the 

 same way, except that 18 cows were treated. For charging the 

 vat in this experiment a commercial arsenical dip was used which 

 in concentrated form was said to contain about 9 per cent of cresol 

 salts. In the first two treatments the strength of the solution was 

 about 0.19 per cent arsenious oxide. Subsequently this was raised 

 to approximately 0.22 per cent. The following spring the treated 

 cattle showed an average infestation of 2.5 grubs per head and 

 the untreated ones an average infestation of 3.33 grubs each. During 

 the spring of 1919 another dairy herd was utilized. Thirteen cows 

 representative of the herd in age and breeding were passed through 

 a wading vat at 4-day intervals and 14 cows were utilized as a 

 control. In this case the vat was charged with a commercial coal- 

 tar creosote dip diluted to about 2 per cent. The following season 

 a careful check of the grubs in the treated cattle showed an average 

 of 6.58 per animal, and the untreated animals showed an average 

 of 3.84 grubs each. The following year a similar test was carried 

 out at the same dairy. A count of the grubs present in the treated 

 and untreated groups made on December 30 showed an average of 

 6 per animal in the case of the former group and 8.14 in the latter. 

 In a subsequent examination made on February 7, the treated animals 

 showed an average infestation of 2.75 grubs each and the untreated 

 animals an average of 2.67 each. 



It is possible that better protection would be afforded should the 

 dipping be done every day. It would not be feasible, however, to 

 dip so frequently with the strengths of solutions used and endeavor 

 to cover a greater portion of the legs by having the solution deeper 

 in the vats. In the experiments mentioned, the walking of the cows 

 through the vats, which were 10 feet long at the bottom and 18 feet 

 long at the top, brought the material into contact with the legs con- 

 siderably higher up than the actual depth of the dip (1 foot). In 

 fact it was found that the udders and bellies of the cattle were fairly 

 well drenched, especially on the cows that were inclined to hurry 

 through the vat. 



Imes and Schneider (4-8) have published results of tests with the 

 application of used automobile cylinder oil, sodium silicate, and coal- 

 tar creosote dip by spraying and wading the cattle through vats 



