14 BULLETIN XO. 200, U. S. DEPARTMENT OF AGRICULTURE. 
aerobic fermentation. This method is used to a considerable extent 
in parts of France and Germany and is fully discussed by Ringelmann. 
A cistern is provided into which drain all the liquids from the stables, 
and the manure heap is watered by pumping the liquid manure from 
the cistern from time to time. 
It is the writer's intention here merely to point out that the disposal 
of manure on the platform maggot trap is but a slight modification of 
the method just mentioned. Figure 4 differs from a diagram given 
by Ringelmann only hi the platform and hi the outlets through which 
the drowned larvae may be washed hito the cistern. Here is shown 
the cistern hi which the liquid manure collects. Watering with the 
liquid manure adds to the heap the valuable constituents of the urine 
and promotes the anaerobic fermentation. If it is true, as just 
suggested, that lack of oxygen and the presence of carbon dioxid 
render the manure unfavorable for the development of the larva?, 
it follows that compact heaping and watering, by excluding air and 
increasing the moisture content, also insure the greatest percentage 
of migration. As a matter of fact, compactness and high moisture 
content are the very factors which make the maggot trap most 
effective, whether the explanation is to be found in the temperature, 
or moisture, or lack of oxygen. 
CONCLUSIONS. 
In this paper we have described the structure of, and the method 
adopted in using, a platform maggot trap. All the manure from a 
stable in which three horses were kept was stored on this platform. 
The results obtained during August and September seemed to show 
that at least 98 per cent of the larvae breeding in this manure were 
destroyed. Fly counts made before and after the trap was installed 
indicated an average reduction of from 67 to 76 per cent. That the 
reduction of flies did not correspond to the percentage of larvae 
destroyed was probably due to the presence of several other breeding 
places well within the range of flight. 
Two difficulties were experienced in the practical working of the 
trap, viz, the accumulation of a certain amount of straw and debris 
on the floor under the platform and the breeding of mosquitoes 
in the water used to drown the fly larvae. It was also found that 
low air temperatures hinder migration and consequently decrease 
the efficiency of the trap. 
Among the merits of the maggot trap were mentioned (1) the com- 
paratively small initial cost and absence of money outlay necessary 
for its maintenance, (2) the very small amount of additional time or 
labor required in its operation, (3) the ease with which wagons 
or manure spreaders can be loaded from the platform, and (4) its 
adaptability for use at stables where the daily production of manure 
