Entomotoxicology is the application of toxicological methods and analytical procedures on necrophagous insects feeding on decomposing tissues to detect drugs and other chemical components, and their mechanisms affecting insect development and morphology and modifying the methodology for estimation of minimum time since death. Nicotine is a readily available potent poison. Because of its criminal use, a gas chromatography-mass spectrometry (GC-MS) method for the detection of nicotine in Calliphora vomitoria L. (Diptera: Calliphoridae) was developed and validated. Furthermore, the effect of nicotine on the development, growth rate, and survival of this blowfly was studied. Larvae were reared on liver substrates homogeneously spiked with measured amounts of nicotine (2, 4, and 6 ng/mg) based on concentrations that are lethal to humans. The results demonstrated that (a) the GC-MS method can detect both nicotine and its metabolite cotinine in immature C. vomitoria; (b) the presence of nicotine in the aforementioned three concentrations in food substrates did not modify the developmental time of C. vomitoria; (c) during the pupation period, larvae exposed to nicotine died depending on the concentration of nicotine in the substrate; and (d) the resultant lengths of larvae and pupae exposed to 4 and 6 ng/mg concentrations of nicotine were significantly shorter than those of the control.
1 August 2018 in Journal of Forensic and Legal Medicine
Regulation of forensic practice in many countries prevents the pathologist performing an immediate autopsy. During the period prior to autopsy, the corpse and the insects possibly associated with it are stored in a mortuary with temperatures ∼4°C. When a corpse is found in a late stage of decay, fly immatures may be present as small or large larval masses. The purpose of refrigeration at 4°C is to slow down the decomposition of the corpse as well as the temporary disruption of the activity and development of the bacteria and the necrophagous insects associated with the corpse. The aim of this research is to investigate the growth and development of different larval masses of the blowfly Lucilia sericata (Meigen) (Diptera: Calliphoridae) when stored in a cold environment (4°C). The research was divided into experimental sessions comprising different storage conditions (continuous or cyclic exposure to a cold environment) for immature stages (second and third instar) and included four different sizes of larval mass (∼100, 500, 1,000, and 5,000 larvae) feeding on 4 kg of beef liver and replicated three times. Results show that if the larval mass has a size of ∼5,000 larvae, and the larvae have already reached third instar, then when they are exposed to a cold environment, their development continues. The storage condition at 4°C does not disrupt the development of such larvae. The number of larvae and their instar that make up the larval mass are essential data for the subsequent estimation of a correct minimum postmortem interval.