DESTRUCTION OF FLY LARViE IN HORSE MANURE. 



17 



termine by field experiments whether the amount of nitrogen thus 

 added compensates for the cost of treatment. The cost of the cyana- 

 mid in 100 or 200 pound lots is about 3^ cents per pound. 



The results of two typical open-pile experiments with calcium 

 cyanamid are given in Table IV. The 5-pound application killed 

 82 per cent of the larvae and reduced the number of bacteria mark- 

 edly. The 4-pound application killed 71 per cent of the larvae and 

 reduced the bacteria 50 per cent. In both cases the water-soluble 

 nitrogen, ammonia, and alkalinity were considerably increased. 



Table IV. — Destruction of fly larvae in horse manure — Results with calcium 

 cyanamid — Open-pile experiments (three applications) at New Orleans, La., 

 November, 1913. 





Treatment of 8 bushels of ma- 

 nure with 10 gallons of water. 



Total 

 number 

 of pupae 

 found 

 after 8 

 to 10 

 days. 



Larvse 

 killed. 



Bac- 

 teria 

 per 1 

 gram 

 ma- 

 nure, 

 dried 



at 

 100° c. 







Water extract. 



No 



Manure. 



In per cent of 

 total nitrogen. 



Alka- 

 linity, 

 N/20 





Solids. 



Total 

 nitro- 

 gen. 



Nitro- 

 gen. 



Am- 

 monia 

 nitro- 

 gen. 



H 2 SO< 

 per 100 

 c. c. (5 

 grams 

 ma- 

 nure). 



Series H: 

 1 



o 



Calcium cyanamid, 5 pounds 



Calcium eyammid, 4 pounds. . . 

 Control 



3,500 

 5,500 

 19, 000 



Per 

 cent. 

 81. G 

 71.0 

 



Mil- 

 lions.. 



43 

 75 

 158 



Per 

 cent. 

 31.30 

 30.47 

 27.14 



Per 



cent. 



0.72 



.59 



.43 



Per 

 cent. 



44.44 

 47.46 

 19.54 



Per 

 cent. 



8.89 

 13.56 



6.51 



C.c. 

 7.35 

 8.15 

 5.30 









EFFECTIVE LARVICIDES (BORATES). 



The most favorable results were obtained by the use of borax 

 (sodium borate) and calcined colemanite (crude calcium borate). 

 Both substances possessed a marked larvicidal action and appeared 

 to exert no permanent injury on the bacteria. These two borates have 

 been used in a large number of experiments and the results all uni- 

 formly show a very high larvicidal action, both in cages and open 

 piles, and whether applied in dry form or in solution. 



A comparison of the total number of flies or of pupse from borax- 

 treated manure with the totals from control manure shows a larvi- 

 cidal power of over 99 per cent in nearly all trials. One of the 

 reasons why borax is so effective in reducing the number of flies is 

 due to its toxic effect on the eggs, which do not hatch after contact 

 with this chemical. The piles in one experiment, started on Septem- 

 ber 13, 1913, were examined for pupse on September 25. At this time 

 large masses of eggs of the house fly, perhaps 600 to 800, were found 

 in a borax-treated pile. They were not empty, collapsed shells, but 

 had normal shape and evidently had not hatched. They were some- 

 what discolored, many having a bluish tinge. Some of these were 



