ENTOMOLOGY

SANITARY ENTOMOLOGYTreating 'With Chemicals.-Nearly all maggots of this class of fliesare exceptionally resistant to the action of chemicals. We have foundsome to survive submergence· in v~ry destructive insecticides. Foremanand Graham-Smith, working in England, have found that creosote oil,which is one of the higher distillates from coal tar, is quite efficacious inthe treatment of carcasses. Two things are accomplished-the majorityof the larvre are actually Jlit by the spray and destroyed and decompositionis practically stopped with correspon!ling reduction in odor. Inrecent experiments conducted at the Dallas Laboratory, we have foundthat several American makes ·of creosote oil are excellent for this purpose.Small carcasses thoroughly sprayed before infestation takes place willremain free from infestation, the flies being repelled by the substanceand odor practically prevented. The carcass usually shrinks and assumesa mummified condition. Such creosote oils are manufactured bya number of concerns and usually sold at prices ranging from sixtyfivecents to one dollar per gallon, according to the per cent of coaltar acids contained. Rather high percentage of these ingredients (atleast l!'l per cent) is best.Since direct sunlight is a powerful destructive agent in the semiaridand arid regions, if burning cannot be accomplished, the carcasses shouldbe left in the most exposed place possible--not in a gully under shade asis usual. This will often result in about 85 per cent control.Disposition of Garbage.-The question of garbage disposal has beendiscussed briefly in other .lectures (Chapters X, XI). Nearly all garbageis attractive to blow flies as well as other forms and the bone andmeat scraps become infested. Where incineration is practicable it is·most !lesirable. When fed to hogs the bones should be picked out andplaced in a screened compartment or treated with borax or creosoteoil.Destruction of Flies.-In general the destruction of flies should beconsidered as secondary to the elimination of breeding places, but undercertain conditions this method of attack has its place.Traps.-Various types of traps have been devised f~r destruction offlies but a careful comparison of many different forms in experiments carriedout at the Dallas Laboratory shows that there is much differencein their efficiency and also that some minor changes in the constructionof a trap may greatly improve the size of the catch. As a result ofthese experiments the fly trap described in Farmers' Bulletin No. 784is being recommended by the Bureau. This trap appears to be the bestall round form for catching both house flies and blow flies. Of coursethe framework of the trap need not be made of hoops and barrelheads, as suggested in that bulletin, although those prove very satisfactory.The essential principles are to ,have· the high cone, comparatively