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 
larve or maggots from the eggs in one day. The larve develop 
into pupe 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 
larve or maggots frequently burrow into the earth to pupate. 
The larve also bury themselves in the same manner in an earth 
stable floor. This propensity of the larve 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 114 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 larve 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 
larve 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 larve, while kainit (KCl and MgSO.) possesses 
only slight larvecidal action. In several experiments, Cook and 
Hutchinson found that calcium cyanamid (CaCN,), a substance 
frequently incorporated in commercial fertilizers to furnish 
nitrogen, apparently destroyed about 98 per cent. of the larve 
when applied to manure at the rate of 14 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 increased, so that the actual 
cost is much less. A portion of the acid phosphate may be re- 
placed with kainit without affecting the larvecidal effect and the 
mixture will then contain all the essential elements of plant food. 
Unfortunately, calcium cyanamid can be purchased only in car- 
