Field Measurements of Stable Fly (Diptera: Muscidae) Demography, Fecundity, and Survival Based on Daily Trap Catches at a Beef Farm in Southern Ontario Over a 5-yr Period

We sampled stable fly, Stomoxys calcitrans (L.), populations using a CO2 baited cloth trap (Nzi trap) each day throughout the summer and autumn at a beef farm near Peterborough, Ontario, Canada, from 1997 to 2001. Females (2,512) were dissected for ovarian age-grading, to produce a demographic profile of farm populations. The number of follicles were counted to produce fecundity estimates. The developmental periods of adult female stages, measured as accumulated degree-days above 10 degree C, were determined for a lab colony of stable flies. These measurements were used to calculate survival in terms of degree-days of the farm populations each year. Of the 2,512 females caught, 42.4% were nulliparous on average each year. The median follicle size at insemination was 305 mu m in the field populations, and 495 mu m in the colony. Farm caught females had an average of 49.15 follicles per ovary overall, with the body size (leg length) and fecundity increasing slightly with age. On average, 44.5% (SE 3.2%) of nulliparous females survived to become parous, and of these, 45.7% (SE 2.1%) survived the uniparous state to become multiparous. Years of higher rainfall had increased fecundity; rainfall did not appear to affect survival.