408 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



INSECTS AFFECTING THE HEALTH OF MAN AND DOMESTIC 



ANIMALS. 



The screavworm and blowflies. — Investigations under this proj- 

 ect have been continued at the field stations of the bureau located at 

 Dallas, Uvalde, and Sonora, Tex. Certain phases of this work have 

 been carried on in cooperation with the Bureau of Chemistry and 

 the Texas Agricultural Experiment Station as heretofore. 



Tests of the efficacy of several different types of traps, bait 

 pans, and baits under range conditions have been continued. The 

 conical screen trap advocated by the bureau is now being rather 

 generally used in the worst screwworm districts of the Soutliwest 

 with very satisfactory results. Experiments carried out during the 

 fiscal year indicate that where wild animals, such as rabbits and 

 prairie dogs, may be obtained readily for bait they may be more 

 economically used than commercial dried baits, especially if they 

 are kept moist and maggot breeding is prevented by surrounding 

 the bait in the pan with water containing borax or nicotine sul- 

 phate. By the use of these larvicides, the attractiveness of the 

 bait is prolonged, since it is not so promptly destroyed by the 

 maggots. Further experiments with commercial dried egg have 

 been carried out. It has been found that this forms a very satis- 

 factory and reasonably priced bait when each bait pan is charged 

 with 6 ounces of dried egg to which have been added 5 grams of 

 sodium carbonate and 1| quarts of water. 



Experiments with larvicides for use in destroying screwworms 

 and other maggots in wounds on livestock have been continued. As 

 a result of this work it has been found that benzol (100 per cent) 

 is very promising. It is not only reasonable in price, but destroys 

 the larvae well, does not have a deleterious effect on the wound, and 

 has good keeping qualities. 



Extensive tests have been carried on with various chemicals with 

 a view to securing suitable repellents for use in keeping flies from in- 

 festing wounds. Experiments with meat placed in jars under 

 close observation have been continued on an extensive scale, and 

 many of the most promising repellents have been tested on live- 

 stock under range conditions. Among the most promising mix- 

 tures thus far discovered are furfural 1 part, commercial pine-tar 

 oil 3 parts, and safrol 1 part, medium pine tar, 3 parts. Several 

 of the lighter pine-tar oils have shown marked repellent effect. 

 It is planned to test on wounds the whole pine-tar series in com- 

 bination with other repellents. 



The ox wakble or grub of cattle. — This project has been contin- 

 ued along the lines indicated in previous reports. Further in- 

 formation of considerable economic value has been obtained on 

 the biology and seasonal history of the two species of warbles in 

 different parts of the country. A few preliminary experiments have 

 been inaugurated to determine the damage caused by this insect, 

 especially on dairy cattle. 



Some educational work incidental to the investigations has been 

 done with a view to showing the livestock raisers the importance of 

 the control or eradication of this pest. As a result of this year's 

 work no information has been gained which indicates that eradication 

 on a county basis as planned will not prove successful if properly 

 financed. 



