Developmental rates of Chrysomya megacephala larvae (Diptera: Calliphoridae) reared on different tissues and temperatures

Insects and other arthropods, when associated with decomposing bodies, can provide useful information on the causes and circumstances of death. Some of the uses of forensic entomology are: The estimate of the postmortem interval (PMI), the determination of possible causes of death and whether the body was moved. Environmental variables and rearing substrate, among others factors, can influence the development rate of insects, thus leading to errors the estimate of the PMI. Several studies have focused on the development of the insects at different temperatures and kinds of tissues used as rearing substrates. However, only a few works analyzed both factors combined. This study aimed to evaluate the developmental rates of Chrysomya megacephala (Fabricius, 1794) (Diptera: Calliphoridae) larvae reared at different temperatures and tissues. Larvae were reared at 25 ± 1°C, 30 ± 1°C and 35 ± 1°C and the tissues used as rearing substrates were Liver, Lung and Muscle of the domestic pig Sus scrofaL. (Artiodactyla: Suidae). Each experimental group was composed of one tissue at one temperature, totaling nine groups. For each group, 10 larvae were individually weighted every 12 h until the larvae reached the pupal stage. A two-way ANOVA was performed to compare the effect of the two variables on larval development, using Larval Weight as a response variable. The Tukey Multiple Range test was used to compare the means. Significant differences in larval weight were observed for the two variables: Temperature (F=10.05; p<0.0001) and Tissue (F=6.42; p=0.0017). No significant interaction between the two independent variables was observed (F=0.54; p=0.7068). The highest adult emergency rate and larval viability were at 30°C (76% and 73.6% for Liver; 80.2% and 73.3% for Lung; 68.6% and 47.5% for Muscle, respectively). The larvae reared in the Lung substrate gained more weight, followed by Liver and Muscle, respectively. There was a significant variation in developmental times among the different temperatures (96h for 35ºC, 108h for 30ºC and 156h for 25ºC). These differences, if not taken into account, can lead to errors when estimating the PMI.