Background: Forensic insects are considered of significant practical value in criminal investigations and serve as a vital biological tool in determining the post-mortem interval (PMI). 
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Methods: The field study conducted in an arid rural area of Wasit Province demonstrated clear differences in the succession of forensic insects between sheep and dog carcasses. 
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Result: Muscidae were recorded as the earliest colonizers during the fresh stage, with higher abundance on dogs compared to sheep, reflecting the influence of skin thickness and the presence of fur on the rate of colonization. During the bloating stage, Calliphoridae represented the primary and most abundant colonizers, with their highest prevalence on sheep carcasses, indicating their rapid sensitivity to gaseous odors. Throughout the active and advanced decay stages, Dermestidae were prominently observed, particularly on dog carcasses, due to their ability to feed on dried tissues and hair remnants. In the final stage (advanced decay), Acari were dominant, associated with the accelerated desiccation of tissues under solar radiation. Meanwhile, Formicidae were present across all stages as opportunistic colonizers, without a specific association with any particular stage. These findings highlight that host type (sheep/dog) and environmental factors (temperature, humidity and sunlight) were decisive elements in shaping the speed of succession and species diversity. The study emphasizes that understanding succession patterns in arid environments provides a crucial basis for developing accurate models to estimate the postmortem interval (PMI) in forensic investigations.

Comparative Study of Forensic Insect Succession on Animal Carcasses in Arid Rural Environments