Temperature-Dependent Development of Nitidula rufipes (Linnaeus, 1767) (Coleoptera: Nitidulidae) and Its Significance in Estimating Minimum Postmortem Interval

SIMPLE SUMMARY: The decay of human or animal carcasses usually attracts the colonization of large numbers of car-rion-related arthropods, especially Diptera and Coleoptera. Since insects are ectotherms, their colonization and development on carcasses are strongly temperature-dependent and predictable, rendering them a powerful tool for estimating the postmortem interval. Nitidulidae is a large family of common storage and agricultural pests of forensic significance. In this study, the development of the sap beetle Nitidula rufipes (Linnaeus, 1767) was observed under seven constant temperatures between 16 and 34 °C to describe the growth and morphology as well as survival rates of the different developmental stages using multiple scientific imaging and statistical techniques. We showed that N. rufipes can complete its development at temperatures between 16 and 34 °C, where the longest developmental time is 71.0 ± 4.4 days at 16 °C and the shortest is 20.8 ± 2.4 days at 34 °C. Body length measurements combined with morphological characteristics allowed for larval aging and instar discrimination, thus providing relatively complete developmental data for N. rufipes. This information serves to aid forensic investigators in determining the postmortem interval of carcasses using N. rufipes. ABSTRACT: Coleoptera, including the family Nitidulidae, are valuable for estimating long-term postmortem intervals in the late stage of body decomposition. This study showed that, under seven constant temperatures of 16, 19, 22, 25, 28, 31, and 34 °C, the developmental durations of Nitidula rufipes (Linnaeus, 1767) from oviposition to eclosion were 71.0 ± 4.4, 52.9 ± 4.1, 40.1 ± 3.4, 30.1 ± 2.1, 24.2 ± 2.0, 21.0 ±2.3, and 20.8 ± 2.4 days, respectively. The morphological indexes of body length, the widths of the head capsules, and the distance between the urogomphi of the larvae were measured in vivo. The regression model between larval body length and developmental durations was simulated for larval aging, and the head capsule width and the distance between the urogomphi at different instars were cluster-analyzed for instar discrimination. Based on the developmental durations, larval body length and thermal summation data were obtained, and the isomorphen diagram, isomegalen diagram, linear thermal summation models, and curvilinear Optim SSI models were established. The lower developmental threshold and thermal summation constant of N. rufipes evaluated by the linear thermal summation models were 9.65 ± 0.62 °C and 471.40 ± 25.46 degree days, respectively. The lower developmental thresholds, intrinsic optimum temperature, and upper lethal developmental threshold obtained by Optim SSI models were 10.12, 24.15, and 36.00 °C, respectively. The study of the immature stages of N. rufipes can provide preliminary basic developmental data for the estimation of minimum postmortem interval (PMI(min)). However, more extensive studies are needed on the effects of constant and fluctuating temperatures on the development of N. rufipes.