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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
positive response. To keep them from wandering back into the darkened 
jar after emerging into the light, it is necessary to transfer the emerged 
individuals into stock bottles as soon as this can be accomplished 
conveniently. 
After a sufficient number of flies have been taken out, they may be 
studied and used for certain experiments. This is best done by etheriz¬ 
ing 1 the insects. Care must be taken not to bring the liquid ether in 
direct contact with the flies, otherwise, they will not recover. The 
stock bottle is held towards the light for a moment, in order to drive the 
flies to the far end, it is then opened and a sufficient amount of ether 
dropped on the cork. The flies soon become etherized and may be kept 
in a state of light anesthesia for from ten to fifteen minutes. During 
this time they may be counted, identified as to species and sex, or studied 
further. After these procedures, the mass of flies may be used in whole 
or in part for experiments, or they may be used to start a fresh brood. 
If the insects are to be used for breeding purposes, approximately 
an even number of both sexes are transferred to a fresh breeding jar 
previously sterilized 2 and prepared with the medium. They are fed for 
the first time after complete recovery from the anesthesia, but the writer 
has found that flies will not take much food until the day following this 
treatment. In order to obtain a large crop the succeeding generation, 
feeding must be practiced for about two weeks or until the majority of 
the females are seen to be ovipositing. In general, it has been the prac¬ 
tice at this laboratory to cease feeding the adults when newly hatched 
maggots are seen to be working within the medium. After the feeding 
is stopped the adults soon die or they may be extracted and killed. 
The best types of food for the adult flies will be described later under 
the sections dealing with the individual species. Certain conditions of 
the food and method of feeding are, however, applicable to the three 
species. All food is prepared under sterile conditions and is stored on 
ice in bottles or test tubes until used. With the exception of lump 
sucrose, employed as one of the essentials for house flies, all foods are 
in a liquid or semi-liquid state, and are warmed to about 37°C. or 38°C. 
before using. By means of sterile pipettes drops of the food are deposited 
over the entire surface of the wire gauze top of the breeding jar. Three 
large drops deposited in each spot are usually sufficient to permit part of 
Chloroform kills many insects even when lightly administered. 
2 Between broods the jars, tops and corks must be cleaned, scrubbed and sterilized. 
The sterilization is practiced for the reason that otherwise bacteria pathogenic to 
flies may be transferred from one brood to another. 
