A comparative study of the reproductive biology and age distribution of house flies (Musca domestica) on dairies in southern California, Minnesota, and Georgia

House fly (Musca domestica) populations were examined in 2004 and 2005 at six dairies in thee climatically distinct regions: southern California, Georgia, and Minnesota. The ages from 511 pairs collected in copula were determined using pterin analysis. Mating males were less than 2 d of age. Mean female age ranged from 20-46 degree-days (2.5-4 d). Mating females had eggs with partial yolk deposition (stage 2 and 3), and 99.2% of females were nulliparous, but remating of females occurred. The cuticular hydrocarbon profiles of females were examined using gas chromatography, with emphasis on (Z)-9-tricosene. Presence of (Z)-9-tricosene was 71% for mating females from California, 63% for Minnesota and 27% for Georgia. (Z)-9-tricosene may not be required for mating.;Numbers of flies were determined from California traps containing 5 mul, 50 mul, or 100 mul of (Z)-9-tricosene, 50 mul of ( Z)-9-tricosene plus sugar, sugar alone or nothing. More males than females were collected at all the treatments. (Z)-9-tricosene baited traps collected more males and females than traps without ( Z)-9-tricosene, but female ages were equivalent (range 86.1-107.5 degree-days).;House flies were netted from each dairy on four days in 2004 and 2005 at predawn, midmorning, noon and midafternoon. The sex ratios and the ages and hydrocarbon profiles of females from each time/location combination were analyzed. At predawn, adults were primarily in the overnight/resting sites. Males and females were equally abundant at feed sites. Males dominated in basking sites and gravid females in oviposition/immature development sites. Young females were under-sampled. Females required a mean of 53.1-95.3 degree-days, based on the dairy, to mature eggs, suggesting that oogenesis was resource-limited at some dairies.;In 2006, age structure changes were used to assess the effectiveness of insecticide treatments. In a 9-week study, one dairy in each state was treated in weeks 4-6 with Tempo-UltraRTM spray in the overnight/resting sites and QuickBaytRTM in the feeding sites. During the treatment period, a reduction in mean degree-day age, spot-card activity, daily survival, and expectation of life was observed as compared to the pretreatment period at treated farms in California and Minnesota.