164 SANITARY ENTOMOLOGY 



the pans should be scalded and then emptied, and rebaited, every three 

 days. 



Fly Paper. — Sticky fly paper has distinct merits and in the presence 

 of abundance of flies should be used. The hanging pyramid strips are 

 considered better by some sanitarians than the flat papers. 



Poisoned Baits. — Many fly poisons are on the market. Any kind of 

 poisoned bait is dangerous in the presence of children or ignorant persons 

 as there are many recorded fatalities to children from drinking fly liquids 

 or licking poisoned papers. 



Phelps and Stevenson, 1917,^ have given a very thorough presentation 

 of the question of fly poisons. Their bulletin should be consulted by any 

 one desiring to go very far into this phase of the subject. 



The most efficient strength of formaldehyde is 0.5 to 1 per cent, which 

 is equivalent to 1.25 to 2.5 per cent of the 40 per cent solution sold as 

 formalin. 



A muscicide considered by them as even superior Jto formaldehyde in 

 many 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. This 

 was made up in stock solution as follows : 



Dissolve 4.95 grams pure sublimed arsenious oxide AsgOg and 20 

 grams pure sodium carbonate in about 300 cc. of distilled water by heat- 

 ing. When the solution is complete the liquid is cooled to 20° C. 

 and the volume made up to 1,000 cc. vith distilled water. Ten cc. of the 

 stock solution are diluted to 1,000 cc. with distilled water and this is 

 called by them the standard arsenite solution, or one-thousandth normal 

 solution. 



Sodium fluoride solution, 1 per cent, gave a mortality equal to that 

 of the standard arsenite solution. 



An interesting feature of their investigation was the reduced eff^ective- 

 ness of these poisons with lowered temperatures. 



Fly Sprays. — In the armies flies often congregate in tremendous 

 numbers and some kind of spray is necessary to kill them. Maxwell- 

 Lef roy handed me the following formula : 



1 tablespoon formaldehyde. 



% pint lime water. 



% pint water. 



Kirk recommends as a spray in latrines and tents a light oil mixed 

 with 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 green- 

 houses is serviceable. 



^ Experimental Studies with Muscicides and Other Fly Destroying Agencies Hy- 

 gienic Lab., Bull. 108. 



