There is very little information concerning carrion fly population genetic structure. We regina (Meigen), from sites spanning the contiguous United States. Analysis of molecular variance (AMOVA) based oil 232 loci found significant variation (Phi(SC) = 23%) among discrete samples (those collected at it bait ill one location over it short period of time). Samples collected in the same location but at different times were also distinct. When samples were pooled into geographic Legions (east, central, west), the variation was negligible (Phi(CT) = 0%). A Mantel test found only a very weak correlation between individual genetic and geographic distances. Relative relatedness coefficients based oil shared allele proportions indicated individual samples were likely to contain close relatives. F. regina arriving at all individual carcass typically represent a nonrandom sample of the population despite a lack of geographic structure. A female blow fly produces hundreds of offspring at one time; therefore. newly emerged siblings may respond in concert to an odor plume. These results may be of interest to forensic entomologists, many of whom use a laboratory colony founded from it small sample for the growth studies that support casework. Discrepancies between published growth curves may reflect such random differences ill the founding individuals.