February, '22] WELLS, bishopp & laake: derris 93 



one to five, one ounce per animal applied with a gun. Three received 

 derris and flour one to ten, 16.2 grams per animal applied with a gun, 

 and two derris and flour one to twenty, 28.75 grams per animal applied 

 with shaker can. These calves, with the exception of one treated with 

 the 1 to 10 mixture, were examined on Feb. 24. All of the lice were killed 

 on the animals treated with the 1 to 10 and only a few were found on 

 one of those treated with the 1 to 20 mixture. All of the others had 

 a few living specimens present although some of them were weak. 

 On Feb. 24, 1921, 16 calves, most of which were lightly infested with 

 L. vituli, were treated with sodium fluoride^ and derris equal parts with 

 a gun. On March 9 and subsequent dates not a living louse could be 

 found and the eggs were collapsed. At Lafayette, Ind. two heavily 

 infested calves were dusted with pure derris and three with equal parts 

 deiTis and flour, applied with a shaker about one ounce of powder per 

 animal. Examinations made four and eighteen days later showed no 

 live lice and all eggs collapsed. 



On Feb. 14, 1921, two calves with a moderate infestation of 5. capil- 

 latus were dusted with one ounce of a mixture of derris and flour, one 

 to five, with adust gun. Two days later one of these showed a few alive 

 and the other about fifty percent killed. On March 1, both were ap- 

 parently free from lice and all of the eggs appeared to have hatched or 

 collapsed. On March 9, however, a group of lice was found near one 

 of the ears. On Feb. 14, a calf was treated with one ounce of derris 

 and flour, one to twenty with a shaker can. Two days later no live 

 lice were found and examination on March 1 showed no living specimens, 

 but several were found to be alive when the animal was examined on 

 March 9. Six calves, each with a lig.ht infestation of 5. capillatus, 

 were treated on Feb. 14 with derris and flour, one to ten, 16.2 grams 

 per host with a dust gun. On March 1, only two living specimens could 

 be found, and on March 9 no adults were present, but several half grown 

 lice were seen. A cow showing a heavy infestation of this species was 

 thoroughly treated with derris and flour in equal parts by means of a 

 shaker on March 1, one and three-fourth ounces of the mixture being 

 used. On March 9 a thorough examination indicated that the lice 

 were completely destroyed. All eggs were either hatched or collapsed. 



All of the calves in these tests were associated with other animals 

 and the re-occurrence of specimens in some cases indicates that the ani- 

 mal may have been reinfested from other stock. 



A test with derris and flour one to one was made on a dog heavily 

 infested with the sucking louse, Linognathus setosus Olfers. The anima 1 

 was given a thorough treatment with one ounce of the mixture with 



^Sodium fluoride has been found to have practically no effect on this species. 



