Diurnal Flight Activity of House Flies (Musca domestica) is Influenced by Sex, Time of Day, and Environmental Conditions

Abstract

House flies (Musca domestica L.) are common synanthropic pests associated with confined animal operations, including dairy farms. House flies can cause substantial nuisance and may transmit human and animal pathogens. Surprisingly little is known about the daily flight activity of house flies. This study examined diurnal house fly flight activity on two southern California dairies using clear sticky traps to capture flies over hourly intervals. Flight activity for both males and females combined started near dawn and generally increased to a single broad activity peak during mid to late morning. Male flight activity peaked earlier than female flight activity and this separation in peak activity widened as mean daytime temperature increased. Flight activity for both sexes increased rapidly during early morning in response to the combined effects of increasing light intensity and temperature, with decreasing flight activity late in the day as temperature decreased. During midday, flight activity was slightly negatively associated with light intensity and temperature. Collection period (time of day) was a useful predictor of house fly activity on southern California dairies and the diurnal pattern of flight activity should be considered when developing house fly monitoring and control programs.

Keywords: California; dairy; light intensity; temperature; trap; wind speed.

Figure 1

Diagrammatic sketches of the dairies and sites sampled. Cattle are held in separate pens collectively indicated by areas with solid grey shading. (A) BS Dairy: Three traps were placed into each of 4 trapping areas (dark grey diagonal striped area) ranging from just west of the dairy center to the eastern edge of the dairy (12 traps per day). (B) OS dairy: Twelve traps were placed randomly each day within the trapping area (dark grey diagonal striped area), at locations where facility workers and cattle would not interfere with them.

Figure 2

(A) sticky panel trap used to capture flying house flies; (B) house fly stuck to adhesive surface of sticky trap; (C) house fly that appears to have flown directly into the adhesive surface of the sticky trap.

Figure 3

Total female (solid) and male (dotted) house flies collected during each collection period on each date. Panels are arranged from lowest (top left) to highest (bottom right) mean daytime temperature.

Figure 4

Number of male (square) and female (triangle) house flies collected in relation to environmental variables for each collection period when averaged over all collection dates. Figure 4 illustrates how fly activity and environmental variables generally change over the course of a day.

Figure 5

Box plots showing house fly activity for combined sexes by collection period across all sampling dates at the BS dairy and OS dairy. Collection periods were hourly intervals starting from 30 min before civil dawn through civil dusk. Due to shortened day length on dates when the OS dairy was sampled, this dairy lacked period 16 collections. Black squares show the average number of house flies collected.

Figure 6

Proportion of house flies captured on sticky traps that were female during each collection period at the BS Dairy and OS Dairy. Black diamonds indicate raw mean proportions. Sex ratio was not significantly different after Tukey’s correction of the p-value (α = 0.05) for collection periods with the same letter.

Figure 7

Collection period with peak house fly flight activity by mean daytime temperature for male (grey; squares) and female (black; triangles) house flies. Shaded bands around each line indicate the 95% C.I. by fly sex.

Figure 8

Predictors of house fly activity near Dawn, through Midday, and near Dusk. Each panel shows the relationship of house fly activity with measured environmental variables: light intensity, temperature, wind speed, and humidity. For environmental variables to which the fly sexes responded similarly, data are combined into single regression line with data points indicated as grey circles. When significant differences by sex were observed for an environmental variable, the data are separated for males (dashed lines; squares) and females (solid line; triangles). Light grey bands around each line indicate the 95% C.I. for each fitted regression line. Non-significant environmental factors are indicated by N.S.