DESTRUCTION OF FLY LARV^ IN" HOESE MANURE, 1915. 13 



it takes 0.25 gram of dicyandiamid to produce the fatal result. The 

 fatal doses for dogs when administered internally are, respectively, 

 0.75 and 2 grams. These experiments indicate that cyanamid is 

 three times as toxic as dicyandiamid. 



SUSPENSIONS OF CALCIUM CYANAMID. 



As the substances which have been found to be effective larvicides 

 act most effectively when applied in solution or suspension, it was 

 considered advisable to test the effect of 3 and 4 per cent solutions 

 of calcium cyanamid. The results of these experiments are recorded 

 in Table 4, Nos. 16 and 17, and Table 6, Nos. 1 and 2. 



The results recorded in Table 4, Nos. 16 and 17, can hardly be 

 compared with the other open-pile experiments for the reason that 

 only 2 bushels of manure instead of 4 were used at each treatment. 

 In No. 16 the application was made twice; that is, there was a total 

 of 4 bushels of manure in the pile instead of 12 as in other experiments. 

 In No. 17 only one application was made to each of the 2-bushel piles. 

 Moreover, only large larvae, probably 3 days old, were present in the 

 manure at the time of treatment. It is not clear how much these 

 conditions .would influence the effectiveness of the solution used, but 

 at any rate the larvicidal results were all low and irregular, except in 

 one experiment, No. 17-B. 



In series 2, Table 6, where two treatments were applied to each 

 of 4 bushels of manure, in duplicate, one result was rather low (80 per 

 cent), while one was fairly good (90 per cent). In series 1, Table 6, 

 cages were not placed over these piles to catch emerging flies, but 

 an estimate of the larvicidal effect was made from examination of 

 the piles on the third day after treatment. At that time no larvae 

 were seen in 1A and only one or two in IB, while the control 

 piles were seen to be heavily infested. In general, the results with 

 solutions of cyanamid were not uniformly favorable, as far as larvi- 

 cidal action is concerned, and it would require a considerable number 

 of additional experiments to determine just what strength would be 

 uniformly effective. 



The bacteria of series 1 and 2, Table 6, showed an increase in 

 three of the four treated samples. No increase of total nitrogen 

 was found, and but one sample, 2A, showed an increase in alka- 

 linity. . The water-soluble nitrogen, ammonia nitrogen, and amid 

 nitrogen in the water extracts of the treated samples of both series 

 showed a tendency to increase. Nitrates were detected in all sam- 

 ples of series 2, but were absent from all samples in series 1. In 

 the former series the manure was older, the piles having stood longer 

 before the samples were taken than with series 1. 



