PREVENTIVE MEDICINE 345 



with a layer of hot manure eight inches in depth. The manure pit, 

 if properly treated, affords a ready means of destroying countless 

 numbers of fly larvae with but little effort. The addition of 

 chemicals to manure with the idea of destroying the eggs and larvae 

 is contraindicated, as Roubaud points out that the fermentation of 

 the manure is delayed, with the result that the period of infestation 

 may be prolonged. 



In addition to the destruction of eggs and larvae, efforts should 

 be made to destroy the adult flies. 



Various methods have been recommended for this purpose, 

 including the following : The manure pit may be covered with 

 leafy branches which have been sprayed with a poison bait composed 

 of arsenite of soda, 6 ozs. ; sugar, 4 Ibs. ; and water 4 gallons. 

 The young flies as they are hatched out settle on the leaves and 

 feed on the poison. Flies may be destroyed in buildings such as 

 stables and cow byres by fumigation with sulphur when the animals 

 are out. Three per cent, of formalin in sweetened milk placed 

 about a room in shallow vessels, such as soup plates or saucers, 

 is calculated to destroy a number of the pests; a piece of bread 

 should be placed in the centre of the dish for the flies to alight 

 on and from which they can suck up the poisoned liquid. If the 

 strength of formalin is greater than 3 per cent, the flies will not go 

 near it. Fly papers and traps are all useful. The following pre- 

 scription for making " Tanglefoot " is taken from Lelean's Sanita- 

 tion in War : Heat together 5 parts of castor oil and 8 parts of 

 powdered resin (both by weight) until the resin is completely dis- 

 solved; the mixture should not be brought to the boil, but should 

 be applied while hot, or heated before application (as thinly as pos- 

 sible), to the surfaces to be coated. Tanglefoot may be spread on 

 glazed paper, strands of wire, hoop iron, &c., which should then be 

 hung in suitable places and be removed when necessary. 



Many sprays and washes have been tried on horses and cattle 

 to ward off flies. As the result of experiments Cory recommends 

 spraying milch cows with a 3 per cent, solution of pine-tar creosote 

 in caustic soda solution. Two-thirds of a pound of soda is dis- 

 solved in water for every gallon of creosote to be emulsified. The 

 emulsion is effective for one day only, but affords some protection 

 for three or even four days.* 



WARBLE FLIES. 

 The Warble flies belong to the genus Hypoderma, of the family 



*Journ. Econom. Entom., 1917, Vol. X., p. Ill, through Vet. Rev., 1917, 



Vol. L, p. 457. 



