Study on the pupal morphogenesis of Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae) for postmortem interval estimation.

Chrysomya rufifacies (Macquart) is one of the most common species of blow flies at the scene of death in Southern China. Pupae are useful in postmortem interval (PMI) estimation due to their sedentary nature and longer duration of association with the corpse. However, to determine the age of a pupa is more difficult than that of a larva, due to the fact that morphological changes are rarely visible during pupal development. In this study, eggs of C. rufifacies were reared in climatic chambers under four different constant temperatures (20, 24, 28 and 32°C each±1°C, respectively) with same rearing conditions such as foodstuff, substrate, photoperiod and relative humidity. Ten duplicate pupae were sampled at 8-h intervals from prepupae to emergence under the different constant temperatures, respectively. The pupae were sampled, killed, fixed, dissected and with the puparium removed, the external morphological changes of the pupae were observed, recorded and photographed. The morphological characters of C. rufifacies pupae were described. Based on the visible external morphological characters during pupal morphogenesis at 28°C±1°C, the developmental period of C. rufifacies was divided into nine developmental stages and recorded in detailed description. Based on above-mentioned nine developmental stages, some visible external morphological characters were selected as indications for developmental stages. These indications mapped to 8-h sampling intervals at the four different constant temperatures were also described in this study. It is demonstrated that generally the duration of each developmental stage of C. rufifacies pupae is inversely correlated to appropriate developmental temperatures. This study provides relatively systematic pupal developmental data of C. rufifacies for the estimation of PMI. In addition, further work may improve by focus on other environmental factors, histological analysis, more thorough external examination by shortening sampling intervals, PAE (the Pupal Age Estimator) method and parasitic insects of C. rufifacies.