Same, same but different!-matching entomological traces to a human food source by stable isotope analysis

Area of Science:

• Forensic Entomology
• Isotope Ratio Mass Spectrometry
• Stable Isotope Analysis

Background:

• Blow flies are crucial in forensic entomology for estimating the postmortem interval (PMI) using immature stages.
• Estimating PMI using adult blow flies or empty puparia is challenging due to potential alternative food sources.

Purpose of the Study:

• To investigate the utility of stable carbon (δ13C) and nitrogen (δ15N) isotopes in adult blow flies (Lucilia sericata) and empty puparia to trace their larval food sources.
• To determine if isotope signatures in adult flies and puparia reflect the isotopic composition of the tissues on which they developed.

Main Methods:

• Comparison of δ15N and δ13C signatures in human and 12 other tissue types using elemental analyzer-isotope ratio mass spectrometry (EA-IRMS).
• Analysis of δ15N and δ13C signatures in adult Lucilia sericata and their empty puparia, reared on various tissues.

Main Results:

• The isotope signatures (δ15N and δ13C) of adult blow flies and empty puparia linearly mirrored the isotope signatures of their larval food sources.
• This linear relationship indicates that isotope analysis can reveal the nutritional history of the flies.

Conclusions:

• Stable isotope analysis is a valuable tool for inferring the nutritional history of blow flies, supporting PMI estimation in forensic investigations.
• It is recommended to analyze entomological traces alongside muscle tissues of potential donors or other food sources for comprehensive dietary analysis.