4 BULLETIN 118, U. S. DEPARTMENT OF AGEICULTUEE. 



The top of the cage is ?-*^»oden door which is fastened down 

 tightly with hinges and hasps. In the center of this door is an open- 

 ing 5 inches In diameter and above this a board provided with two 

 openings of the same size. Cone-shaped flytraps are fitted into these 

 openings. This board is placed in grooves so that either one of the 

 two traps may be brought over the opening in the door by merely 

 sliding the board. 



On one side of the cage is a small trapdoor 5 inches square through 

 which samples of manure may be taken out for examination. 



Each cage stands on legs 4 inches high and in a galvanized-iron 

 pan 3 feet square with sides 4 inches high. This pan serves to collect 

 drip water and escaping larva?, and to isolate the cage from such 

 predatory insects as ants. 



Eight bushels of manure were used in each of the cage experi- 

 ments. It was dumped in at the top and the chemical, in solution, 

 was sprinkled on with a watering can. After two preliminary ex- 

 periments it was found necessary, in order to insure thorough pene- 

 tration, to use 10 gallons of the liquid per 8 bushels; that is, at the 

 rate of 1 gallon to 1 cubic foot. Usually the sprinkling was done in 

 three layers by putting 2 bushels of manure in the cage and apply- 

 ing 2-J gallons of the solution. This was repeated in the second layer 

 of 2 bushels. Finally, the remaining 4 bushels were added and the 

 last 5 gallons of the solution applied. When a chemical was applied 

 in dry condition it was scattered over the surface of the manure, 

 which was treated in three layers as in the case of the solution; 10 

 gallons of water were afterwards added. 



The manure in the control cages was sprinkled with water equal 

 to the volume of the solutions of the chemicals used. In this wav 

 the moisture content of the manure was made as nearly as possible 

 the same in all cages. It will be understood that 10 gallons of 

 solution were applied to 8 bushels of manure in all the cage experi- 

 ments mentioned below, unless some other explanation is given. 

 After treatment in this way the doors of the cages were closed and 

 the flytraps put in place. The cages were examined every day. The 

 escape of any larvae into the drip pan was noted, and the volume 

 of the drip water measured and a sample analyzed. A quart sam- 

 ple of manure was removed through the small door at the side of 

 the cage after a day or two and the percentage of living and dead 

 maggots determined. The larval counts of quart samples were 

 very unsatisfactory so far as indicating the comparative larvicidal 

 value of the chemicals, but the results of some of these counts are 

 given in the tables. 



After five to seven days flies began to emerge, and then it was nec- 

 essary to darken the cages with black cloth tacked on the sides, as seen 



