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Cook (F. C), Hutchison (R. H.) & Scales (F. M.). Experiments in 

 the Destruction of Fly Larvae in Horse Manure. — U.S. Depf. Agric, 

 Washington, D.C., Bull. no. 118, 14 July 1914, 26 pp., 4 pis., 

 7 tables. 



This is an account of a series of investigations made to find a 

 chemical that will destroy Musca domesticn in its principal breeding 

 place, horse manure, without injuring the bacteria or reducing the 

 fertihsing value of the manure. A brief survey of former experimental 

 work on this subject is given and the method of these investigations 

 described. Where possible, three properties of the chemical under 

 examination were determined : (1) The larvicidal power, determined 

 by the percentage of larvae killed ; (2) the bactericidal power, deter- 

 mined by the percentage of bacteria killed ; (3) the chemical effect 

 of the substance on the manure. The method of these determinations 

 was as follows : The manure to be examined was put into a cage 

 consisting of a wooden framework of inside measurement 2 by 2 

 by 4 ft., to which 2 layers of bronzed wire screening were attached 



2 in. apart. Each cage stood on legs, to isolate it from predatory 

 insects, and was placed in a galvanized iron pan, into which excess 

 liquids drained, through holes in the bottom of the cage, any chance 

 larvae that fell through these being counted. The top of the cage was 

 a tightly fitting wooden door, with openings over which cone-shaped 

 fly traps were fitted ; there was a small trap-door on one side of the 

 cage, through which samples of manure could be taken. In most 

 experiments 8 bushels of manure were put in at the top of the cage, 

 10 gallons of the chemical solution were sprinkled on the manure in 



3 layers ; when a dry chemical was used it was scattered over the 

 surface of the manure in 3 layers, 10 gallons of water being then added. 

 The manure in the control cages was sprinkled with 10 gallons water, 

 to make the moisture content of all samples as nearly as possible 

 the same. After sprinkhng, the cage doors were closed, the fly-traps 

 put in place and when the flies began to emerge, the whole cage, except 

 the entrance to the fly trap, was darkened. The flies caught in the 

 traps were chloroformed and counted daily, the difference between 

 the numbers of flies from a cage of treated manure and from a control 

 cage is taken as an index of the larvicidal effectiveness of the chemical ; 

 bacterial and chemical analyses were made of samples taken from the 

 treated and untreated manure; special precautions were taken to 

 obtain uniform samples, but no small samples can be taken that will 

 be truly representative. A parallel series of experiments, simulating 

 natural conditions, was carried out by treating manure piles on the 

 ground. In this way 24 different chemicals were tried at various 

 concentrations ; only 7 showed any effective larvicidal action in the 

 strengths used and borax seems to be the most economical, practical 

 and effective of them all. The experimental results are briefly as 

 follows : — Kerosene emulsion, no appreciable larvicidal action and 

 useless on a large scale ; kainite, no larvicidal power, in an open 

 pile experiment the bacterial count was 17*5 against 5"9 in the control, 

 indicating a stimulating action of the compound on the bacteria, 

 chemical analyses showed an increased amount of ammonia and the 

 possible production of nitrates and nitrites ; pyroligneous acid, little 

 if any repellent or larvicidal power ; Isthmian Canal Commission's 



