First report of the presence of Necrodes littoralis (L.) (Coleoptera: Silphidae) on a human corpse in Italy

Abstract The colonization of a human body by Necrodes littoralis (L.) (Coleoptera: Silphidae) is reported for the first time in Italy. This species is both necrophagous and predator of necrophagous fauna. The body colonized by the coleopteran was found indoors, in an advanced decomposition stage, in a suburban area of Cosenza (Calabria, Southern Italy) in November. Insects (adults, puparia and larvae) were collected on and around the body. Puparia and larvae were raised in the laboratory until the adult stage for morphological identification, which was carried out through taxonomical keys. Besides N. littoralis, also the presence of Calliphora vicina Robineau‐Desvoidy, Chrysomya albiceps (Wiedemann) (Diptera: Calliphoridae), Hydrotaea dentipes (Fabricius) (Diptera: Muscidae), and Creophilus maxillosus (L.) (Coleoptera: Staphylinidae) was detected. Necrodes littoralis is a species of forensic interest because it may colonize human and vertebrate corpses and has been reported elsewhere in Europe.


| INTRODUC TI ON
Among insect orders, Coleoptera are relevant for forensic investigations, together with Diptera. Some species of this order directly feed on corpses but others predate necrophagous fauna, interfering with the colonization of remains. Forensic entomologists rely both on age of immature insects found on corpses and on the arthropod successional pattern associated with different decay stages [1][2][3][4][5].
Necrodes littoralis (L.) (Coleoptera: Silphidae) is of forensic interest because it colonizes and breeds on human and vertebrate remains.
This necrophagous species is also a predator of dipteran larvae [6,7]. Although common in Europe, it has never been reported in Italy as colonizer of human bodies. Here, we describe for the first time the presence and activity of N. littoralis on a well-decomposed human corpse discovered indoors in an abandoned sports facility in a suburban area of Cosenza (Calabria, Southern Italy).

| DISCUSS ION
This is the first report on the presence of Necrodes littoralis on a human body in Italy. The other dipteran species found on the body, C. vicina and Ch. albiceps and the coleopteran Cr. maxillosus have already been reported on human bodies in Italy, the first two indoors and outdoors, and the third only outdoors [12][13][14][15][16][17][18]. Concerning H. dentipes, this species was previously found on a human body in Northern Italy, see Grzywacz et al. [19], but it has been found for the first time in Southern Italy during this study. Among Coleoptera, the species belonging to the family Silphidae are widely distributed around the world. The family is divided into two subfamilies, Silphinae and Nicrophorinae [3], and includes about 210 species, 44 of which are present in Italy [20]. Silphidae are scavengers that contribute to recycling organic matter [21] and are able to consume dead vertebrates [22]. They are frequently found on human remains [7, [23][24][25] and on experimental animal models [26][27][28][29]. Several forensic studies have reported their presence in insect successional patterns but little attention has been devoted to their role as forensic indicators in human cases [27,30].
The species has been reported in Italy on animal carrions and in pitfall traps with rotting meat bait [36]. Concerning human bodies, many cases of colonization by N. littoralis have been reported outside Italy. Larvae and adults of this species were found in Spain in the soil near a body of a young man, and adults were found on the body during the autopsy [37]. In France, the species was found in 154 forensic cases out of 1028, examined from 1990 to 2013 [7].
According to this study, the species mainly reached the corpses during the advanced stages of decomposition and only rarely during the other stages. In Poland, N. littoralis was found on human bodies in 2015 [38] and 2017 [39]. Outside Europe, N. littoralis was found on a human corpse discovered in a forest area in South Korea [40].