Colonization pattern and thermal needs of immature phases of Sarcophaga argyrostoma (Diptera: Sarcophagidae): Significance for estimating postmortem interval

Abstract

Members of Sarcophagidae are necrophagous and are commonly found on decaying carcasses; and their developmental forms are important indicators for the approximation of lowest postmortem interval (PMImin). This work describes the biological characteristics of Sarcophaga argyrostoma from Tehran, Iran. Various temperature regimes were applied to estimate the thermal summation constant (k) and thermal requirements for development of S. argyrostoma. Five growth proceedings, containing 1st ecdysis, 2nd ecdysis, wandering, pupariation and eclosion, were investigated under eight fixed temperature regimes (6–30 °C). The effects of fly age, freshness, and availability of oviposition substrate on oviparity and viviparity was studied. At 6 °C, no development occurs, and at 8 °C only the first ecdysis occurs. At temperatures between 10 and 30 °C, all immature stages proceeded to the adult stage, and thus immature development was analyzed at these six remaining temperatures. The development phases needed minimum (Dz ± SE) 5.4(0.4), 8.5(0.26), 5.3(0.44), 3.8(0.1), and 6.6 (0.6)°C to attain one of the succeeding developmental occasion, correspondingly. The approximated K for those five occasions were 15.04 ± 1.12, 12.62 ± 0.65, 140.36 ± 4.35, 14.59 ± 0.6, and 222.8 ± 4.18°-day (DD) accordingly. When the food substrate is available and fresh, the female prefers to lay eggs, no matter how old she is. However, the chance of ovoviviparity increased when no oviposition substrate was available. The truth that S. argyrostoma able to either larviposit or to lay eggs encompasses serious consequences for the precise estimation of the PMImin, as the existence of larvae resulting from eggs laid on the carcass could add hours (based on ambient temperature) to the PMImin.