In the city of Savannah, Georgia, which has an estimated population of 130,000 people, surveys were conducted to determine the present sources of house flies and blow flies in the city.
Fly dispersal tests were conducted using laboratory-reared flies of a yellow-eyed mutant strain of the common blow fly Callitroga macellaria. These tests indicated that this species of fly would move readily from the city dump back into the city proper. Tests conducted under rather adverse weather conditions with respect to fly activity showed that this species would travel in all directions from the point of release in the city and for distances up to 1½ miles within seven hours.
Results of the fly release tests and surveys of fly breeding sources indicated that the city garbage dump, located approximately 3 miles from the heart of the business district, was the principal source of flies in the city. Garbage cans and dog feces were the only important sources of fly breeding found in residential areas. Fly breeding in the “garbage sludge” accumulated in the bottom of garbage containers, or in the soil under inadequate or unserviceable containers, was found to occur in approximately 60 per cent of all containers examined. The percentage of containers involved in active fly production at the time of survey in the various typical urban areas was 69 per cent in the best residential area, 62 per cent in the middle-class section, 56 per cent in the tenement district, and 61 per cent in the business district. The percentage of premises found positive for fly breeding in dog stools was 41 per cent in the best residential area, 20 per cent in the middle-class section, and 7 per cent in the tenement district.
All privies in the city probably produce flies, but the number of privies in the city is small. Abattoirs, poultry houses, and stables are high producers of flies, but such establishments are not numerous. No significant fly breeding was found at fertilizer plants, grocery stores, creameries, feed stores, or neighborhood chicken yards.
The relative importance of the various fly breeding sources in cities will vary with local conditions, and each city should be the subject of a thorough survey by competent observers in advance of attempting municipal fly control.
No fly breeding sources in Savannah were observed which could not be reduced greatly or eliminated entirely by improved sanitation practices.
Considering the added benefits of partial control of rats, roaches, and other vermin of public health importance which would accompany fly control by improved sanitation, and the appearance in widely separated areas of strains of flies resistant to DDT and certain other insecticides, it seems appropriate to reemphasize and strongly recommend sanitation as an important, effective, and economical means of municipal fly control.
Communicable Disease Center, Public Health Service, Federal Security Agency, Atlanta, Ga.