A number of conditions which may influence the survival of the fly were studied under experimental laboratory conditions. One feeding a day of milk and sucrose was found to be sufficient for maintaining the flies. Water, when offered, was rejected most of the time and did not significantly increase the survival time (ET50). Caged flies under normal insectary conditions lived considerably longer than did immobilized test flies.
In general, multiplication of E. coli did not appear to take place in the insect's alimentary canal. Somewhat over 50 per cent of the bacteria ingested were recovered. There was no significant difference in bacterial output by the flies fed on diets containing different amounts of sucrose in skim milk, although this would have had to be great in order to be significant because of the variations in the total counts within the diets. Almost all the bacteria were released by the time of the ET50.
E. coli was tagged with radioactive P32 and fed to the flies. For several days thereafter there was fairly good correlation between the radioactive and bacterial counts.
The flies' rate of uptake of E. coli was determined under laboratory conditions. The maximum number of bacteria was found after 45 to 60 minutes. Following this, there was an apparent decrease for approximately 5 hours; then there was an apparent increase, indicating a revisit by the fly to the source of the organisms.