ENTOMOLOGY

164 SANITARY ENTOMOLOGYthe pans should be scalded and then emptied, and rebaited, every threedays.Fly ·Paper.-Sticky fly' paper has distinct merits and in the presenceof abundance of flies should be· used. The hanging pyramid strips areconsidered better by some saniturians than the fiat papers.Poisoned Baits.-Many fly poisons are on the market. Any kind ofpoisoned bait is dangerous in the presence of children or ignorant personsas there arc many reco'rded fatalities to children from drinking fly liquidsor licking poisoned papers. .Phelps and Stevenson,,1917,2 have given a very thorough presentationof the question of fly poisons. Their bulletin should be consulted by anyone desiring to go very far into this phase of the subject.The most efficient strength of formaldehyde is 0.5 to 1 per cent, whichis equivalent to 1.~5 to ~.5 per cent of the 40 per cent solution sold asfonnalin.A muscicide considered by them as even superior.to formaldehyde inmany ways is an aqueous solution of 1 per cent sodium salicylate plus 10. per cent brown sugar.They used sodium arsenite as the basis for their experiments. Thiswas made up in stock solution as follows:• Dissolvr 4.95 gra"!s pure sublimed arsenious oxide AS 2 0 3and ~ograms prl~e sodium carbonate in about 300 cc. of distilled water by heating.When the solution is complete the' liquid is cooled to ~oo C.and the '!"'olume made up to 1,000 cc. with distilled water. Ten cc. of thestock solHion are diluted to 1,000 cc. with distilled water and this iscalled by h 'II the standard arsenite solution, or one-thousandth normalsolution.Sodium flu,nide solution, 1 per cent, gave a mortality equal to thatof the standard trsenite solution.An interesting feature of their investigation Was the reduced effectivenessof these poisolls with lowered temperatures.Fly Sprays.-In .:'he armies flies often congregate in tremendousnumbers and some ki. -I of spray is necessary to kill them.Lefroy handed me the following formula:1 tablespoon formaldehyde.1h pint lime water.1h pint water.Maxwell­Kirk recommends as a spray in latrines and tents a light oil mixedwith three or four parts of water well shaken. Rubber tubing should.not be used in the spray. A coarse atomizer such as is used in greenhousesis serviceable.• Experimental Studies with Muscicides and Other Fly Destroying Agencies, HygienicLab., Bull. 108.