Temperature-dependent appearance of forensically useful flies on carcasses

Area of Science:

• Forensic Entomology
• Thanatology
• Insect Ecology

Background:

• Current postmortem interval (PMI) estimations rely on insect larval or pupal age, providing only a minimum PMI.
• Estimating the pre-appearance interval (PAI) is crucial for advancing forensic entomology.
• Carrion beetle PAI is temperature-dependent, suggesting potential for temperature-based PAI estimation in flies.

Purpose of the Study:

• To investigate the relationship between adult or oviposition PAI and temperature for nine European fly species.
• To determine if temperature alone can be used to estimate PAI in flies, similar to carrion beetles.

Main Methods:

• Collected PAI data from pig carcasses decomposing under varied temperatures.
• Analyzed the relationship between adult and oviposition PAI and prevailing temperatures for nine fly species.
• Utilized regression analysis to assess temperature-PAI correlations.

Main Results:

• Adult PAI of *Hydrotaea dentipes*, *Hydrotaea ignava*, *Hydrotaea similis*, *Phormia regina*, and *Stearibia nigriceps*, and oviposition PAI of *S. nigriceps* showed an exponential relationship with temperature.
• *Stearibia nigriceps* exhibited a strong temperature-PAI correlation, indicating potential for temperature-based estimation.
• PAI for *Calliphora vomitoria* and *Hydrotaea pilipes* showed no temperature relationship.
• *Lucilia sericata* and *Lucilia caesar* displayed a distinct low-temperature response, with PAI increasing sharply at low temperatures and remaining stable at higher temperatures.

Conclusions:

• Temperature alone is a reliable predictor for PAI in *Stearibia nigriceps*.
• Different fly species exhibit varied responses to temperature regarding PAI, likely due to distinct colonization times and decomposition stages.
• Further research is needed to understand the diverse mechanisms influencing PAI and temperature in forensic entomology.