Análise do perfil químico cuticular de imaturos e adultos da mosca varejeira de importância forense Chrysomya megacephala (Calliphoridae: Diptera): implicações para estimativa do intervalo pós-morte

Abstract

Forensic entomology is the study of the insect fauna applied to legal context related issues. Diptera is the major order and the most studied, and Calliphoridae, known as "blow flies" are considered the most important family to forensic entomology, since they are usually the first insects to locate carcasses and perform oviposition. These insects are used to the main application thereof in legal context, the estimation of minimum postmortem interval (PMImin). However, there are several obstacles to get an accurate estimate, be it by the fact that samples are in poor condition, making it impossible for rearing for subsequent identification, or that there are no identification keys that cover all immature flies of forensic interest, etc. In this sense, multiple studies suggest cuticular hydrocarbons as a complementary taxonomic tool to help get faster results to solve forensic skills. These compounds are a constituent part of the lipid layer, and seem to have emerged by the need of the insect to avoid water loss, and later evolved to chemical communication. It is known that they are species-specific, acting as a "fingerprint" of the insect. Although it is known that these compounds can be used as a useful tool for forensic entomology, studies using this technique in our country are still rare. Therefore, the aims of this study were: 1) Determine the chemotaxonomic profile and intraspecific variation of cuticular hydrocarbons of a fly of forensic interest. 2) Assess whether chemical compounds of pupal exuviae of flies of forensic interest of different waves of oviposition could be used to expedite the results of forensic skills. 3) Test the effectiveness of an alternative technique to assess differences in the composition cuticular chemical profiles on samples of forensic interest. Samples of flies were collected from two distinct populations and their cuticular compounds evaluated by two different techniques. According to the results, cuticular compounds can be used to distinguish both the instar, and the population of origin of samples, having important implications in determining the PMI and location where the crime occurred. Chemical compounds of the exuviae of different generations can provide reliable results to assist in the field of criminal expertise. The results of the alternative techniques show that they can be used and, since there is no need of sample preparation it can speed up even more the criminal skills.