Mortality rate, reproductive output, and trap response bias in populations of the blowfly Lucilia sericata

1. The ages of 877 females of the blowfly Lucilia sericata, collected from two farms in south-west England between May and September 1996, were determined using a combination of ovarian dissection and wing fray analysis. 2. Using survivorship analysis, the mortality rates over the entire field season were estimated to be 2.2 and 1.9% per day-degree at the two farms, respectively. These gave a mean life expectancy of 46 and 53 day-degrees, and a lifetime reproductive output of 130 and 172 eggs per female. 3. The mortality rate remained relatively constant over time, with one exception, the first sample of the season when no older flies were present, indicating that underlying changes in demography (emergence and senescence of generations) over the field season were not sufficient to affect the rates calculated by survivorship analysis. 4. The response of L. sericata to liver-baited traps was affected strongly by age and reproductive status, with gravid females and females in the early stages of ovarian development being most markedly over-represented relative to other age categories.