The effect of seasonal and geographic variation on early carcass colonization by forensically important blow flies (Calliphoridae) in British Columbia.

Using a terrestrial-based field study, the abundance and diversity of necrophagous insects were monitored over a nine-month period within distinct environments in the Metro Vancouver region of BC, Canada. Acting as body proxies, small baited bottle traps (n=9) were deployed weekly for 12-hour intervals in three different environments, accumulating a total of 1334 specimens. Collected specimens were analyzed microscopically to determine species ID, sex, and gravidity. Ambient temperature and precipitation data for each site was obtained from the nearest government weather station. Following the same procedures, a second component of the study analyzed the influence of light intensity on carcass colonization by placing bottle traps (n=9) in shaded areas at each site. Bivariate analyses revealed significant relationships between species, geographic location, and month of collection, suggesting that necrophagous species composition is influenced by habitat type and seasonal shifts in temperature. Sex ratios, reproductive ranges, and light preferences of Calliphoridae were examined.