202 SANITARY ENTOMOLOGY 



Treating with Chemicals. — Nearly all maggots of this class of flies 

 are exceptionally resistant to the action of chemicals. We have found 

 some to survive submergence in very destructive insecticides. Foreman 

 and Graham-Smith, working in England, have found that creosote oil, 

 which is one of the higher distillates from coal tar, is quite efficacious in 

 the treatment of carcasses. Two things are accomplished— the majority 

 of the lan^ae are actually hit by the spray and destro^'ed and decomposi- 

 tion is practicall}'' stopped with corresponding reduction in odor. In 

 recent experiments conducted at the Dallas Laboratory, we have found 

 that several American makes of creosote oil are excellent for this pui-pose. 

 Small carcasses thoroughly sprayed before infestation takes place will 

 remain free from infestation, the flies being repelled by the substance 

 and odor practically prevented. The carcass usually shrinks and as- 

 sumes a mummified condition. Such creosote oils are manufactured by 

 a number of concerns and usually sold at prices ranging from sixty- 

 five cents to one dollar per gallon, according to the per cent of coal 

 tar acids contained. Rather high percentage of these ingredients (at 

 least 12 per cent) is best. 



Since direct sunlight is a powerful destructive agent in the semiarid 

 and arid regions, if burning cannot be accomplished, tlie carcasses should 

 be left in the most exposed place possible- — not in a gully under shade as 

 is usual. This will often result in about 85 per cent control. 



Disposition of Garbage. — The question of garbage disposal has been 

 discussed briefly in other lectures (Chapters X, XI). Nearly all gar- 

 bage is attractive to blow flies as well as other forms and the bone and 

 meat scraps become infested. Where incineration is practicable it is 

 most desirable. When fed to hogs the bones should be picked out and 

 placed in a screened compartment or treated with borax or creosote 

 oil. 



Destruction of Flies. — In general the destruction of flies should be 

 considered as secondary to the elimination of breeding places, but under 

 certain conditions this method of attack has its place. 



Traps. — Various types of traps have been devised for destruction of 

 flies but a careful comparison of many diff^erent forms in experiments car- 

 ried out at the Dallas Laboratory shows that there is much difl'erence 

 in their efficiency and also that some minor changes in the construction 

 of a trap may greatly improve the size of the catch. As a result of 

 these experiments the fly trap described in Farmers' Bulletin No. 734* 

 is being recommended by the Bureau. This trap appears to be the best 

 all round form for catching both house flies and blow flies. Of course 

 the framework of the trap need not be made of hoops and barrel 

 heads, as suggested in that bulletin, although those prove very satis- 

 factory. The essential principles are to have the high cone, comparatively 



