Diurnal and nocturnal observations of fly resting habits in urban areas were made in the vicinity of Pharr, Texas, from January 1950 to June 1951 and in Savannah, Georgia, during a short period in the summer of 1950.
M. domestica was the most numerous species observed at Pharr, followed in order of numerical importance by Sarcophagula occidua, Drosophila spp. (repleta and melanogaster), and Phaenicia spp. (mostly pallescens and sericata). In Savannah Phaenicia pallescens was by far the most numerous species observed, with M. domestica second and Sarcophaga sp. third.
In both areas, ground surfaces and scattered garbage were the principal day-time resting surfaces for all observed species except Drosophila. Likewise, grasses, weeds, trees, and shrubs represented the most important nocturnal resting surfaces for all species except Drosophila.
The observations on Drosophila were confined entirely to the Pharr area. During the day, most of the Drosophila were found in privy pits, whereas at night most of them were observed on privy ceilings.
Based on these studies, residual spray operations for urban fly control should include the treatment of grasses, weeds, shrubs, the lower limbs of trees, the interior of privies, and garbage cans and their immediate environs. In the Pharr area, the interior of utility buildings should also be included. The spraying of outbuildings or the outsides of any structures was not indicated.
The high concentration of flies in preferred resting places at night suggests that selective space spraying of these resting places at night might give more efficient fly control than present daytime space spraying procedures.
The presence of great numbers of Drosophila in privies raises the question of their possible role as filth flies and disease vectors and emphasizes the need for further studies to determine their status in relation to the transmission of disease.