Studies were conducted in the lower Rio Grande Valley of Texas to determine the importance of fly production from privy pits and garbage can sites. House fly production from dieldrin-treated privies was shown to exceed greatly that found in untreated privies. Dieldrin resistance in M. domestica appeared to influence house fly breeding in privies more so than any other single observed factor, the emergence of M. domestica apparently increasing concurrently with the development of the resistance. The increased production of house flies in treated privies presents an important and immediate problem in the future prevention and spread of enteric diseases. Abandoned privy pits produced more flies than did garbage can sites but approximately 50 per cent of the emerging flies were Sarcophaga spp.
At garbage can sites approximately 96 per cent of the flies produced were Phaenicia pallescens. Fly emergence was greater at “approved” can sites than at “non approved” sites, indicating that proper garbage handling within the containers is vital in preventing fly breeding in garbage containers.