Thermal developmental models of a Chinese population of the blow fly Calliphora vicina Robineau-Desvoidy

Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae) is widely distributed across the Holarctic, Oriental, and Neotropical realms, and has also been introduced to Australia and New Zealand. Numerous case reports confirmed that this species frequently colonizes corpses at death scenes, validating its considerable forensic value. Therefore, investigating the developmental patterns of C. vicina is crucial for estimating the minimum postmortem interval (PMI_min). This study observed developmental duration and larval body length in C. vicina under seven constant temperature conditions (16-34 °C), constructing isomorphen diagrams, isomegalen diagrams, and thermal summation models. The results showed that C. vicina could complete its entire developmental cycle within the temperature range of 16-28 °C. At 16, 19, 22, 25, and 28 °C, the developmental durations from egg to adult of C. vicina were 801.25 ± 6.11, 522.25 ± 6.71, 474.33 ± 10.66, 388.29 ± 4.23, and 384.95 ± 2.83 h, respectively. At 31 °C, C. vicina immatures died during pupariation; at 34 °C, larvae died during the wandering stage, failing to complete the full developmental cycle under both temperature conditions. The thermal summation constant (K) of C. vicina was determined to be 6676.18 degree-hours. The lower threshold temperatures (T_L) calculated by the linear thermal summation model and nonlinear thermodynamic model were 7.52 °C and 7.68 °C, respectively. The nonlinear thermodynamic model further revealed that the upper lethal developmental threshold and intrinsic optimum temperature of C. vicina were 30.11 °C and 19.50 °C, respectively. These findings provide critical data for estimating PMI_min based on the developmental patterns of C. vicina. Using the developmental data, the PMI_min of an indoor death case was successfully estimated.