A comparison of blow fly (Diptera: Calliphoridae) and beetle (Coleoptera) activity on refrigerated only versus frozen-thawed pig carcasses in Indiana

To have large numbers of replicates in forensic entomology research, it is often necessary to freeze carcasses and thaw them before use in experiments. Research on the effects of freezing on decomposition is minimal in the literature and the effect that it has on insect (e.g., blow fly, beetle) activity is virtually unknown. The objective of this study was to compare the differences in insect activity occurring on refrigerated only versus frozen-thawed pig carcasses, and to characterize the associated dipteran fauna. Seven pigs, frozen for 2 mo and then thawed before the experiment, were compared with seven pigs killed and stored in a walk in refrigerator approximately 12 h before the start of the experiment. No significant differences in time to the appearance of adult flies, eggs, larvae, or the initiation and conclusion of larval migration were observed between refrigerated only and frozen-thawed pig carcasses. Beetles from the family Staphylinidae also did not show a significant difference in arrival times. Phormia regina (Meigen), Lucilia coeruleiviridis (Macquart), Cochliomyia macellaria (F.), Pollenia rudis (F.), and Hydrotaea leucostoma (F.) comprised the dipteran taxa present on the carcasses. Results suggest that freezing pigs before exposure in the field does not significantly alter blow fly life events or the appearance of staphylinid beetles.