DESTRUCTION OF FLY LAEVJE IN HORSE MANURE. 11 



CRESYLIC ACID. 



Cresylic acid, which is prepared from coal tar, was tried in dilu- 

 tions of 1 to 20, 1 to 40, and 1 to 80 in cage experiments, but it was 

 without action on the maggots. Bacteriological and chemical anal- 

 yses were made of the manure treated with the 1 to 20 strength, and 

 the bacteria were reduced 90 per cent. The alkalinity of the manure 

 was reduced, and a slight increase in ammonia over that of the con- 

 trols was found. 



PARA-DICHLOROBENZENE. 



Para-dichlorobenzene was employed in two sets of cage experi- 

 ments, using one-half pound and 1 pound to 8 bushels of manure- 

 The substance was ground and scattered over the manure, and water 

 added. As shown (Table I, series 79, A and B, and 98, A and B), the 

 apparent larvicidal effect varied greatly, the one-half pound strength 

 indicating a 50 and 93 per cent action and the 1 pound indicating 78 

 and 97 per cent effectiveness. The bacterial counts and chemical 

 analyses where the one-half pound applications were made showed 

 only slight effects from this treatment. No analyses of the manure 

 in the cages treated with the 1-pound applications were made. Para- 

 dichlorobenzene was tried in one pit experiment. The pits were of 

 concrete with inside measurements of 9 by 6 by 2 feet. Thirty-two 

 bushels of manure were placed in the pits, and the manure in one pit 

 was treated at the rate of 0.5 pound to 8 bushels. The other pit was 

 untreated. From the former 403 flies emerged, and from the latter, 

 484. The larvicidal action was, therefore, apparently about 16 per 

 cent. Duckett (1915) has found this substance to be an effective 

 fumigant against various household insects and those affecting 

 stored products. 



FORMALDEHYDE . 



Further experiments with formaldehyde were performed, using 1 

 to 6, 1 to 8, and 1 to 10 dilutions of the commercial 40 per cent for- 

 malin in water. The 1 to 8 and 1 to 10 strengths showed no larvi- 

 cidal effects, and the action of the 1 to 6 solution on the maggots was 

 slight (17 per cent). The bacteriological and chemical results showed 

 the same general tendencies as those found last year, an increased 

 number of bacteria and a reduction of the alkalinity being observed. 

 As the cost of formaldehyde is high, and as strong solutions are re- 

 quired to kill the maggots, the use of this substance is not practical 

 for this purpose. 



NITROBENZENE. 



Nitrobenzene (C 6 H 5 N0 2 ), commercially known as oil of mirbane, 

 costs 20 cents per pound and contains 11.4 per cent of nitrogen. The 

 vapors of this liquid are poisonous. Two sets of cage experiments at 



