DAIRY INSPECTION 163 



manure, but when this is not available the eggs are deposited 

 in other organic material. The heat generated by the decom- 

 position processes which occur in such material hatches the 

 larvae or maggots from the eggs in one day. The larvae develop 

 into pupae in 4 to 5 days and flies emerge 3 to 4 days later. The 

 time from the egg to the fly is 8 to 10 days. 



It is recommended that manure be removed to the fields at 

 intervals of seven days or less to prevent the development of 

 the flies, but this plan will be effective only when the manure is 

 stored in a receptacle which has a tight bottom, because the 

 larvae or maggots frequently burrow into the earth to pupate. 

 The larvae also bury themselves in the same manner in an earth 

 stable floor. This propensity of the larvae to migrate has been 

 made use of to trap them by Hutchinson, who constructed a 

 trap consisting of a raised platform with a shallow cement tank 

 beneath it. The platform is made of wood strips 1% inches 

 thick and 1 inch wide, laid 1 inch apart. The manure is piled 

 compactly on the platform, each day's addition being moistened 

 with water. When the larvae are hatched they migrate down- 

 ward and fall through the spaces in the platform into the water 

 in the tank below, where they are drowned. 



Numerous experiments have been made to discover a sub- 

 stance which when mixed with horse manure would destroy the 

 larvae of the house-fly without affecting the fertilizing value 

 of the manure. Naturally, the chemical fertilizers were tested, 

 but it was found that acid phosphate and ground phosphate rock 

 will not kill the larvae, while kainit (KC1 and MgSO 4 ) possesses 

 only slight larvaecidal action. In several experiments, Cook and 

 Hutchinson found that calcium cyanamid (CaCN 2 ), a substance 

 frequently incorporated in commercial fertilizers to furnish 

 nitrogen, apparently destroyed about 98 per cent, of the larvae 

 when applied to manure at the rate of % pound to the bushel 

 with an equal quantity of acid phosphate. The cost of this 

 treatment is 1.8 cents per bushel of manure, but the fertilizing 

 value of the manure is considerably in creased, so that the actual 

 cost is much less. A portion of the acidi phosphate may be re- 

 placed with kainit without affecting the larvaecidal effect and the 

 mixture will then contain all the essential elements of plant food. 

 Unfortunately, calcium cyanamid can be purchased only in car- 



