Rapid discrimination of maggots utilising ATR-FTIR spectroscopy

Abstract

Entomological evidence is used in forensic investigations to indicate time since death. The species and age of maggots or flies that are present at the scene can be used when estimating how much time has passed since death. Current methods that are used to identify species and developmental stage of larvae and fly samples are highly subjective, costly and often time consuming processes and require the expertise of an entomologist or species identification via DNA analysis. The use of vibrational spectroscopy, as an alternative identification method, would allow for a quicker, cheaper and less subjective technique and would allow entomological evidence to be used more commonly in the forensic process. This proof of principle study shows the potential for using attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) as a rapid tool for differentiating between various species of larvae, such as those commonly found at crime scenes. The proposed regime would provide a rapid and valuable tool resulting in reduced time for both species identification and life cycle determination, particularly in forensic situations.

Preprocessing methods for near‐infrared spectrum calibration

“…Several preprocessing schemes are selected for evaluation based on the summary in Table 1: Single preprocessing schemes: None, SG, SG1D, SG2D, MC, AS, SNV, MMN, RNV25, RNV50, RNV75, AN, VN, MSC, OSC, NAS, and ALS; these count as 17 methods. SGxD followed by MC, AS, SNV, MMN, RNV25, RNV50, RNV75, AN, VN, MSC, OSC, NAS, or ALS; these count as 39 methods. MC, AS, SNV, MMN, AN, VN, MSC, OSC, NAS, or ALS followed by SGxD; these count as 30 methods. The methods contained in the second group and the third group can be frequently found in the literature. OSC + normalization 56 : OSC + MC, OSC + AS, OSC + SNV, OSC + VN, OSC + AN, OSC + MMN; these count as six methods. The two‐method permutations composed of VN, MC, SNV 32,50,52,54,55 count as 6 methods. Other methods include AN + SGxD + MC, 59 SGxD + AN + MC, 58 MSC + SGxD + MC, 25 and ALS + SNV 49 ; these count as 10 methods. …”

Prediction of mosquito species and population age structure using mid-infrared spectroscopy and supervised machine learning

“…In particular, near-infrared spectroscopy (NIRS) has been evaluated as a general strategy for examining insects since it does not require reagents and holds promise as a fast, practical, non-destructive, and cost-effective method for entomological surveillance. The results obtained to date have proved that the chemical composition of mosquitoes and other insects not only changes between species 39– 41 , also across different age 40, 42– 45 , according to resistance to insecticides 46 and in the presence of an infectious agent 47, 48 . While promising, the NIRS typical approach has certain drawbacks.…”

Spectral Signatures of Immature Lucilia sericata (Meigen) (Diptera: Calliphoridae)

“…Very recently, hyperspectral remote sensing has shown beneficial impact in forensic entomology by rapidly discriminating blow fly species at the larval stage [43]. Also, pushbroom hyperspectral imaging to age Calliphora dubia Macquart and Chrysomya rufifacies Macquart puparia measured dorsally and ventrally has now been completed to refine the puparial stage based on development of adult morphological characteristics [20].…”