February, '22] wells, bishopp & laake: derrts 91 



In our tests of the substance when applied externally on animals 

 and fowls we have seen no indication of any poisonous effects to the host. 

 It is also stated that in factories where the roots are being powdered the 

 employees become covered with the dust and experience no ill effects 

 whatever. It is certain, however, that with a material so toxic it is 

 necessary to proceed rather cautiously until we know more about its 

 effects on the higher animals and man. 



The powdered derris roots used in our tests were kindly furnished by 

 the Tobacco By-Products & Chemical Corporation, and is supposed 

 to be from Deguelia (Denis) elliptica. 



Experiments With Derris Against Mallophaga 



In our tests of this material against Mallophaga we treated chickens 

 infested with seven species of lice and cattle infested with the common 

 biting louse of that host [Trichodectes scalaris). Where chickens were 

 rather thoroughly dusted with derris the lice were very quickly destroyed, 

 practically all of them being dead the day following treatment. Sub- 

 sequent examinations extending over a period of six weeks showed no 

 live lice present, thus indicating that the eggs were killed or the young 

 lice destroyed upon hatching. Derris was also tested in suspension 

 in water by Mr. H. P. Wood. Over forty fowls were dipped in a bath 

 containing one-fourth ounce of powdered derris to one gallon of water. 

 Subsequent examinations showed that a few lice were still present on 

 the first and second day after treatment but soon after this all live lice 

 disappeared and none were found on several subsequent examinations. 

 In another test derris was used at the rate of one ounce to three gallons 

 of water. Two and one-half hours after dipping some dead lice were 

 found but a few living ones were present for about two weeks, when all dis- 

 appeared. 



Derris Against the Common Biting Louse of Cattle 



A ntmiber of experiments were carried out with the dusting of cattle 

 with derris diluted with various amounts of carriers. In the preliminary 

 experiments at Dallas, in which the authors were assisted by Mr. H. P. 

 Wood and Mr. E. E. Wehr, the results against this species were not 

 very satisfactory, but these rather indifferent results were chargeable 

 in a measure to the fact that the calves were not thoroughly dusted. 

 In one test three heavily infested animals were treated with derris and 

 tobacco dust, equal parts, the latter containing about .1% nicotine. 

 The material was applied at the rate of 12.3 grams per animal with a 

 dust can. On the following day all but a few scattered lice were dead. 

 Subsequent examinations showed the presence of a few live nymphs 

 only, thus indicating that probably all adults were destroyed but some 



