Musca domesticaL. and other synanthropic diptera were baited with a mixture of Lursect™ fly attractant and dichlorvos sugar bait to detect differences in fly catch among selected stations on 5 southern California poultry ranches.Significant shifts in the spatial response of house fly to bait stations were noted over time on both the east-west and north-south ordinates. House fly catches inside buildings increased with high temperatures, but overall catches were greatest at sunlit perimeter stations at the ends of cage rows.Females were more abundant than males within the poultry houses, but a 1:1 male:female relationship was approached when fly catch was high either in terms of time or space. Between 15–32°C fly catch and the male proportion of the catch was significantly correlated with temperature.An intensive baiting experiment demonstrated differences in spatial response amongM. domestica,Fannia canicularis(L.), andMuscina stabulansFallen. These differences were represented by opposing directional tendencies and clearly defined preferences for bait stations located along the inside wall or at the ends of the cage rows.