Factors affecting accuracy and precision of thermal summation models of insect development used to estimate post-mortem intervals

Abstract

This paper investigates the effects that different summary statistics (minimum, median, mean, or maximum), temporal sampling resolutions (duration between sampling events), and sample sizes (number of individuals sampled per sampling event) had on the accuracy and precision of the regression coefficients of a typical thermal summation model used to calculate minimum post-mortem interval (PMI). No significant differences were found in the values of the developmental constants calculated from different summary statistics of the duration of development. Sample size was found to affect the precision of measurement of the duration of development but had little overall influence on thermal summation constant (K) and developmental threshold (D0) calculations (and therefore, subsequent PMI estimates), but temporal sampling resolution had a direct influence on the accuracy of K and D0 calculations. These data suggest that when numbers of experimental maggots are limited, it is more important to sample more frequently using smaller sample sizes than to sample less frequently with large sample sizes. Furthermore, we suggest that the median is the most representative summary measure of the duration of development and should be used preferentially.

Development Time Variability: Adaptation of Régnière’s Method to the Intrinsic Variability of Belgian Lucilia Sericata (Diptera, Calliphoridae) Population

“…This procedure was repeated at minimum 8 times for each temperature regime except for mortality at 20°C. Successfully emerging adults were recorded daily and removed from the box [14]. threshold (t L ) and thermal constant (Kt) from the median development time at each temperature [13,14].…”

“…Such variability could also result from different experimental designs [6,11]. Furthermore, the given development time are mainly based on summary statistics such as minimum [3,12], median [5,13,14], mean [2,15], maximum [3] or percentage [1,4,16]. The use of these different sampling methods and types of synthetic parameters could bias the accuracy of the final published development data [14].…”

“…Furthermore, the given development time are mainly based on summary statistics such as minimum [3,12], median [5,13,14], mean [2,15], maximum [3] or percentage [1,4,16]. The use of these different sampling methods and types of synthetic parameters could bias the accuracy of the final published development data [14]. Therefore, Wells and Lamotte [17] promote the use of full distributions instead of summary values.…”

“…Interestingly, median is an often used synthetic value and is recommended by Richards and Villet [14] in the context of forensic entomology. A more recent publication suggests a parameter estimation procedure for time distributed delay (TDD) models [19].…”

The effect of environment on development and survival of pupae of the necrophagous fly Ophyra albuquerquei Lopes (Diptera, Muscidae)

“…This has direct implication in the analysis of development data as observed by Ikemoto & Takai (2000) and Richards & Villet (2008). Richards & Villet (2008) call attention to the variation of the thermal constant, necessary to estimate the ADD. This estimate may vary depending on the development measures minimum and maximum.…”