Use of hyperspectral remote sensing to examine immature blow fly development

Medico-legal entomology, the study and application of insect science to criminal investigations, is most notably used to estimate a minimum post-mortem interval (minPMI). Examining blow fly development to make this estimation provides the minimum time it takes to reach the oldest stage associated with the remains. Unfortunately, providing the time it takes to reach a stage may underestimate the age of the insects during the lengthier post feeding stage and intra-puparial period. Hyperspectral remote sensing is introduced as a means to solve this issue and to examine the potential for narrowing these lengthier stages into days within the stages. Hyperspectral remote sensing involves sensing, recording and processing reflected and emitted energy to produce point source measurements. Spectral measurements of both immature Protophormia terraenovae and Lucilia sericata were completed from second instar to adult emergence from the mid-section, anterior and posterior ends of developing immature blow flies. Functional regressions and coefficient functions were examined for model prediction and generalization to identify demarcations within stadia to age the immature blow flies. Aging P. terraenovae larvae was successful at wavelengths ranging from 400-1000nm, however, at that wavelength range, only the last day of the intra-puparial period could be distinguished from the first five days. Immature Lucilia sericata were examined at a wider range of wavelengths (350-2500nm) and model prediction and generalization for both pupae and larvae was possible. Similarities and differences were found between species and potential contributing factors were considered such as range of wavelengths analyzed, food substrate, significance of washing away surface contaminants before measuring, contributions of cuticular hydrocarbons, and potential surface bacteria, best region to measure the immature blow fly and replication experiments. Hyperspectral remote sensing not only allows an entomologist to incorporate more precision in their estimate but error rates are also introduced which is required of a forensic science according to the National Academy of Sciences.