Facultative Viviparity in a Flesh Fly (Diptera: Sarcophagidae): Forensic Implications of High Variability in Rates of Oviparity in Blaesoxipha plinthopyga (Diptera: Sarcophagidae).

Abstract

Flesh flies are major primary consumers of carrion and are commonly found on human remains. Due to this latter feeding habit, their development rates can be used to provide temporal information in forensic investigations. This is usually done by referencing published flesh fly development datasets. Flesh flies are typically assumed to be strictly viviparous and datasets reporting their development rates therefore start at the first larval instar. However, an increasing number of studies has identified oviposition by flesh flies, including the forensically relevant species Blaesoxipha plinthopyga Wiedemann. To assess the impact of egg-laying behavior on casework, oviparity rates and time before larval hatching were assessed under controlled laboratory conditions that reflect common casework conditions in Harris County, Texas. We demonstrated systematic deposition of viable eggs but at a very variable rate between samples. Similarly, the duration between oviposition and larval hatching was highly variable, with some eggs taking more than a day to hatch after deposition. These results highlight the need to account for embryonic development in forensic investigations including B. plinthopyga and advocates for the re-evaluation of the assumed strict viviparity of the Sarcophagidae.