ATR-FTIR spectra of weathered blow fly puparia

The estimation of the weathering time of empty blow fly puparia at a crime scene helps with the estimation of the minimal time since death of the deceased. Since puparia are very durable and can be collected even years after the emergence of the adult flies, they are a key insect trace in long term PMI scenarios.

Empty puparia of four forensically relevant blow fly species (Lucilia sericata, Calliphora vicina, Protophormia terraenovae and Chrysomya albiceps) were weathered under three different conditions for a total duration of up to 9 months. Three biological replicates from different oviposition events were generated. Each month, 10 puparia per replicate and weathering condition were removed, cleaned and measured on an ATR-FTIR spectrometer (JASCO FT/IR-4200 with PIKE Technologies GladiATR accessory). Each puparium was measured four times, each spectrum was normalized via the standard normal variate and the four measurements per puparium were averaged.

Cvic/Cv = C. vicina, Lser/Ls = L. sericata, P.ter/Pt = P. terraenovae, Chalbi/Ca = Ch. albiceps
age = storage/weathering time of the puparia (in words), age2 = storage/weathering time of the puparia (numerical value)
treatment = weathering condition, none = puparia were measured after the emergence of the adult fly, room = puparia were stored under room conditions, leaf litter = puparia were placed on top of soil and covered with leaf litter (outdoors), soil = puparia were buried up to 6 cm deep in soil (outdoors)
R1 - R3 = biological replicate 1 to 3