Chrysomya megacephala (Fabricius, 1794) is the most abundant and predominant species which arrives and colonizes a cadaver first in most parts of China. Therefore, its growth and development patterns have great implications in the estimation of the minimum postmortem interval (PMI_min). In this study, C. megacephala was collected from the Yangtze River Delta region and reared at seven constant temperatures ranging from 16 °C to 34 °C. The developmental duration and accumulated degree hours, larval body length and morphological changes of C. megacephala were examined. Furthermore, we constructed three developmental models, isomorphen diagram, isomegalen diagram and thermal summation model, which can be used for estimating PMI_min. The developmental durations of C. megacephala at 16 °C, 19 °C, 22 °C, 25 °C, 28 °C, 31 °C and 34 °C are (794.8 ± 14.7), (533.2 ± 10.1), (377.8 ± 16.8), (280.8 ± 15.1), (218.9 ± 8.5), (190.8 ± 10.1) and (171.8 ± 6.8) h, respectively. The developmental threshold temperature D₀ is (11.41 ± 0.32) °C, and the thermal summation constant K is (3 418.7 ± 137.0) degree hours. Regression analysis was conducted to obtain equations of the variation in larval body length with time after hatching, and variation in time after hatching with body length. Moreover, our study divides the intra-puparial morphological changes of C. megacephala into 11 sub-stages, and provides the time range experienced by each sub-stage. The results of this study provide fundamental development data for the use of C. megacephala in PMI_min estimations.

Forensic entomologists usually estimate the minimum postmortem interval (PMI_min) using the time required for the oldest immature insects found on the corpse to grow to its development stage and age at the time of discovery. The sheep blow fly Lucilia sericata (Meigen, 1826) is a carrion fly found nearly worldwide, and important in forensics. We studied the development time of L. sericata from egg to adult at constant temperatures of 16, 19, 22, 25, 28, 31, and 34°C, and found that the times required are 913.2 ± 19.4, 588.8 ± 35.8, 459.8 ± 15.2, 373.2 ± 15.3, 308.0 ± 9.7, 272.5 ± 9.2, and 267.5 ± 10.5 h, respectively. We established three development models to infer the age of the immature insect: isomegalen diagram, isomorphen diagram, and thermal summation model. In addition, a regression analysis was performed on the relationship between body length and total development time from hatching to dispersing. The thermal summation constant during the development of L. sericata is 6023.2 degree hours and development threshold temperature is 9.19°C. The results of this experiment provide a basis for the use of L. sericata in the estimation of PMI_min.

Sarcosaprophagous flesh flies are insect species frequently found on corpses, and their developmental patterns can be used as reliable indicators for estimating minimum postmortem interval (PMI_min). In this study, the Boettcherisca peregrina Robineau-Desvoidy was reared at seven constant temperatures ranging from 16 to 34 °C to investigate the indexes of development duration and larval body length. Using these results, we generated three development models, including isomorphen diagram, isomegalen diagram, and thermal summation model. Regression analysis was conducted to obtain simulation equations of the variation in larval body length with time after larviposition, and variation in time after larviposition with body length. The developmental durations of B. peregrina from larviposition to adult eclosion under 16, 19, 22, 25, 28, 31 and 34 °C were 1,064.7 ± 34.8, 756.0 ± 19.0, 559.6 ± 5.5, 414.3 ± 3.9, 315.0 ± 2.0, 278.0 ± 4.0, and 258.0 ± 3.5 h, respectively. The developmental threshold temperature of B. peregrina was 10.87 ± 0.49 °C, and the thermal summation constant was 5,809.7 ± 291.4 degree days. The results of this study provide basic data for the use of B. peregrina for estimating PMI_min.