DESTRUCTION OF FLY LARVAE IN HORSE MANURE. § 



Kainit, which consists of potassium chloric! and magnesium sul- 

 phate, furnished us by Dr. F. Zerban, of New Orleans, was used in 

 two cage experiments and in one open-pile test. In the cage experi- 

 ments 4 pounds of kainit were used. The total number of flies 

 obtained from the treated cages averaged 2,194, and from the two 

 controls 3,104 flies. In the open-pile experiment three applications 

 of 4 pounds per 8 bushels were made, and after 10 days about 12,000 

 pupse were found. The corresponding control pile contained about 

 20,000 pupse. 



In the two cage experiments no chemical or bacteriological exami- 

 nations were made. In the open-pile experiment the bacterial count 

 was high, 17.5 million, as compared with 5.9 million in the control. 

 One hundred c. c. of water extract, equivalent to 5 grams of the 

 manure, from the treated pile contained a trace of nitrites and 

 nitrates. No nitrites or nitrates were found in the kainit, nor did 

 the control manure show any. The ammonia nitrogen in the kainit- 

 treated manure was 12.3 per cent and in the control manure but 8.8 

 per cent of the total nitrogen. The high bacterial count and the 

 increased amount of NH 3 obtained, as well as the fact that nitrates 

 were found in the kainit-treated and not in the control manure, 

 suggests that this compound may have a stimulating action on the 

 bacteria, but no conclusions are justified from this one test. This 

 chemical may be used to reenforce manure, but possesses little larvi- 

 cidal power. 



PYROLIGNEOUS ACID. 



Pyroligneous acid was used in commercial form without dilution. 

 Certain claims have been made in some districts of the South, espe- 

 cially in North Carolina, that pyroligneous acid is of value as a repel- 

 lent, and in our experiments special attention was given to this point. 

 Two piles of fresh manure of 8 bushels each were sprinkled with 

 10 gallons of pyroligneous acid. Before treatment no eggs were to 

 be found anywhere on the surface of either pile. Two hours later 

 fresh batches of eggs were found on both piles. The pupse collected 

 numbered about 6,000 and 8,000. Further observations showed that 

 fly eggs were deposited on other piles of manure treated with the 

 pyroligneous acid. Evidently the pyroligneous acid has little, if 

 any, value as either a repellent or a larvicide. The bacterial counts 

 showed a great increase, rising from 25 million in the control to 653 

 million in one of the pyroligneous acid piles. 



ISTHMIAN CANAL COMMISSION'S LARVICIDE. 



The Isthmian Canal Commission's larvicide, which has been suc- 

 cessfully applied in the Canal Zone for the purpose of killing mos- 

 quito larvae, is prepared according to the following formula: 150 

 45780°— Bull. 118—14 2 



