BUREAU OF ENTOMOLOGY. 409 



A number of tests have been made with the destruction of the 

 warbles in the backs of cattle by applying powders and washes. 

 As a result of this work it has been found that over 98 per cent 

 of the grubs can be killed with a general application to the backs 

 of cattle of powdered derris root. A wash consisting of 1 pound 

 of derris, 4 ounces of soap, and 1 gallon of water has also given 

 a percentage of kill above 96. An ointment consisting of 1 part 

 derris and 5 parts vaseline has also given almost 100 per cent kill 

 when the material was pressed into each hole. Injections of 100 

 per cent benzol with an oil can have also given almost complete 

 destruction of all warbles treated. 



Lice affecting livestock. — Investigations of the life history, 

 habits, and longevity of the biting and sucking lice of the goat have 

 been carried forward in cooperation with the Texas Agricultural 

 Experiment Substation No. 14 at Sonora, Tex. Much difficulty has 

 been experienced in attempting to rear these insects under control, 

 thus making progress slow. Some experiments with the dipping 

 of goats in arsenical solutions of different strength have also been 

 carried out. 



Further tests of insecticides in dry form have been made against 

 cattle lice. In this work the discovery that hellebore when dusted 

 over lousy animals will give complete destruction of both biting and 

 sucking lice is worthy of note. 



Poultry parasites. — Further studies on the biology and control 

 of the stick-tight flea have been carried out at the Uvalde station, 

 and a brief report of the work has been published in the Journal 

 of Agricultural Eesearch. Additional experiments on the control 

 of the common poultry mite and the fowl tick or " blue bug " have 

 been carried out. In this connection some attention has been given 

 to the possibility of destroying these and other external parasites of 

 poultry by administering certain chemicals and chemical compounds 

 in the food and water. 



Malaria mosquitoes. — The clinical and biological investigations 

 of certain experimental control measures, conducted by the Interna- 

 tional Health Board and the bureau, were brought to a close at the 

 end of 1922 upon the completion of the original three-year program. 

 The accumulated notes and records were then taken to Baltimore, 

 where, with the assistance of the department of biometry and vital 

 statistics of the Johns Hopkins School of Hygiene and Public 

 Health, the data were summarized and studied and reports prepared 

 for office records and publication. 



The full report covering this work was divided into the follow- 

 ing sections, the titles of which indicate the field covered by the joint 

 investigation : 



The experimental control units and comparative malaria incidence. 

 A statistical study of the occurrence of malaria in the population as a whole. 

 Collections and comparative abundance of Anopheles in different units and 

 localities. 



Studies of Anopheles infection under natural conditions. 

 The identification of the blood meal of mosquitoes. 

 The blood-feeding habits of malaria-carrying mosquitoes. 

 Preferential feeding experiments with Anopheles. 



Of the above, the last three manuscripts dealing with the blood- 

 feeding habits and host preference of Anopheles were prepared for 



