The number of adult male and female house flies, Musca domestica L. (Diptera: Muscidae), near varying levels of (Z)-9-tricosene alone (5, 50, or 100 µl) or combined (50 µl) with sugar was determined using conical screened traps on a dairy in southern California. Overall, significantly more males than females were collected in the traps. Significantly more flies (male and female) were collected in traps with (Z)-9-tricosene. There were no significant differences among doses of (Z)-9-tricosene alone, but numbers of both sexes were significantly higher in traps baited with (Z)-9-tricosene and sugar compared with the 5- and 50-µl doses without sugar. The age of female flies collected in traps was determined by pterin analysis. Mean female ages ranged from 94.7 to 99.6 degree-days (6.3–6.8 d of age) and did not differ significantly among treatments. Dissections of a subset of females from each treatment determined that collected females were primarily nongravid (86.3%). Proportions of gravid females that were collected did not differ among treatments.