Larval identification key to necrophagous Coleoptera of medico-legal importance in the western Palaearctic

Abstract

Several necrophagous Coleoptera species are frequently collected on cadavers, may occasionally act as intermediate or paratenic hosts of parasites, as vectors of pathogens or as allergens, and can also represent major pests of preserved animal products. However, despite their medical, veterinary and economic importance, there is a lack of reliable species identification tools for the larval stages (usually the only entomological evidence associated with medicolegal investigations), thus severely limiting their potential application as forensic indicators. Here, we provide an identification key to the larvae of the necrophagous Coleoptera species which have been recorded on carrion in the western Palaearctic region, based on easily observable morphological characters. In total, we provide diagnostic characters for the reliable identification of 23 necrophagous Coleoptera species within four different families (Cleridae, Dermestidae, Nitidulidae and Silphidae). In addition to the aforementioned families, we provide diagnostic characters for the identification of the larvae of families Histeridae, Staphylinidae and Trogidae, which can also be collected on cadavers. It is expected that the present key will facilitate the identification of larval material of necrophagous Coleoptera collected either in carrion succession studies or during medicolegal investigations, in order to further advance in the potential use of this insects as forensic tools.

Avoidance of carnivore carcasses by vertebrate scavengers enables colonization by a diverse community of carrion insects

“…Collected adult insects and Coleoptera larvae were frozen prior to preservation and storage in 70% ethanol, whereas Diptera eggs and larvae were fixed by immersion in hot water for ~30 seconds prior to preservation and storage in 70% ethanol to prevent decomposition of tissues and facilitate identification, in accordance with published standards and guidelines [53]. Species identification of the insect material was carried out on the basis of diagnostic morphological characters following available keys [54–58].…”

“…We used Akaike’s information criterion for small samples sizes (AICc) to identify the most parsimonious model (the one with the lowest AICc) and rank the remaining models, calculating ΔAICc as the difference in AICc between each model and the best model in the set. Those models with ΔAICc < 2 were retained as candidate models, as they are considered to have similar support [58]. When we retained at least two candidate models, we evaluated their overall degree of support by calculating their proportion of explained deviance (D 2 ) using the following formula [61]: D 2 = (null deviance–residual deviance) / null deviance * 100.…”

The first record of Omosita nearctica Kirejtshuk (Coleoptera, Nitidulidae) in South Africa, with the first description of its mature larva

“…The description of the urogomphi of O. colon by Hayashi (1978) differs from the description by Díaz-Aranda et al (2018). Hayashi (1978) describes them as short and Díaz-Aranda et al (2018) states they are half the length of the ninth tergite which appears to be more accurate (Fig 9b). It must be noted that the pregomphi and urogomphi are all referred to as urogomphi by Díaz-Aranda et al (2018).…”

“…The morphological character states listed in Table 3 may be used to differentiate the mature larva of O. nearctica from that of O. colon, the only other species of Omosita for which the larva has been described (Eichelbaum 1903;Verhoeff 1923;Hinton 1945;Böving and Rozen 1962;Hayashi 1978;Díaz-Aranda et al 2018). The description of the urogomphi of O. colon by Hayashi (1978) differs from the description by Díaz-Aranda et al (2018). Hayashi (1978) describes them as short and Díaz-Aranda et al (2018) states they are half the length of the ninth tergite which appears to be more accurate (Fig 9b).…”

“…Hayashi (1978) describes them as short and Díaz-Aranda et al (2018) states they are half the length of the ninth tergite which appears to be more accurate (Fig 9b). It must be noted that the pregomphi and urogomphi are all referred to as urogomphi by Díaz-Aranda et al (2018). It is crucial to recognise that because O. nearctica was recognised only in 1987, prior references to O. colon larvae from the Nearctic (e.g.…”