358 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 9 



vessel. Although the garbage juice was not tested as to strength it 

 was known to he acid. 



In all of the work done thus far the eggs as well as the larvae seem 

 unable to develop in acid media, but up to a certain percentage they 

 were found to develop in alkaline media. Tests indicated that acid 

 has strong larvicidal properties. To determine this with more cer- 

 tainty a number of experiments were undertaken. A quantity of 

 fresh horse manure which flies were known not to have laid their eggs 

 upon was secured. Three portions of this were taken, each containing 

 about a quart of solid manure. The first portion was confined under 

 a bell jar with two flies. This manure was untreated. The second 

 portion was confined under a bell jar with twelve flies. This manure 

 was sprayed with a .75 per cent solution of hydrochloric acid. The 

 third portion was divided into four smaller parts. On each of these 

 parts was put a mass of eggs. The whole was then sprayed with a 

 .75 per cent solution of hydrochloric acid. The parts were then con- 

 fined in bottles. All of the cultures were examined from time to 

 time for several days. The results pbserved were as follows: portion 

 1, which had not been treated, was found to contain great numbers of 

 larvae. The second portion, which had been sprayed and confined 

 with twelve flies, contained but four larvae. The third portion, which 

 after being sprayed and impregnated with eggs had been divided among 

 four bottles, was found to have developed larvae in only one bottle and 

 then only in small numbers. The larvae were tiny and had left the 

 manure to crawl about the bottle. Some, however, were unable to 

 get out of the manure and had died. Manure which was well infested 

 with both larvae and eggs was sprayed with .75 per cent hydrochloric 

 acid and placed under a bell jar. At the end of three days many of 

 the larvae were dead and many of the masses of eggs had not hatched, 

 due to their being killed by the acid. Larvae which were not dead had 

 left the manure. Whether any great number of the eggs had hatched 

 is doubtful, although no effort was made to determine this. It is 

 quite probable that eggs just ready to hatch might finish the process 

 even if treated with acid in this way, although the escape of larvae 

 from the manure would be difficult. Many would probablj' die be- 

 fore they could get out of it. Any remaining in the manure would 

 certainly perish. 



Old rags have been more or less discussed, especially by popular 

 writers, as a favorable situation in which flies would breed. A number 

 of rags were moistened and placed with a few flies beneath a bell jar. 

 The flies were found to deposit their eggs upon them and in a few days 

 the eggs hatched. As the rags were relatively clean the larvae were 

 unable to get food, so soon left them. Dr. Hewitt has found (2) flies 



