Necrophagous Insects of Forensic Importance

The faunal inventory on exposed carcasses has already been documented in various geographical locations. The diversity of insects and arthropod populations colonizing corpses and animal carcasses is limited in a burial environment. Different authors (Mégnin 1894; Leclercq 1978; Smith 1986; and others) have highlighted the modification of insect populations between exposed and buried remains.

Amendt et al. (2004) and Gennard (2007) focused on the main families and genus of insects of forensic importance (Table 13.3); therefore Diptera and Coleoptera are the most represented orders on exposed cadavers.

Diptera order showed a great diversity of population. Among the Diptera, Calliphoridae (genus Calliphora, Chrysomya, Cochliomyia, Lucilia, Phormia) and Muscidae (Hydrotaea, Musca, Muscina and Ophyra) are predominant families.

Among the Coleoptera, Silphidae (genus Necrodes, Nicrophorus, Silpha), Staphylinidae, Dermestidae and Histeridae are well represented.

In order to propose a (non-exhaustive) list of insects of forensic importance from buried remains, we compared inventories proposed by Amendt et al. (2004) and Gennard (2007) with different studies (Table 13.4).

The composition of populations might be divided into five main categories of depths: very shallow, shallow (10-30 cm deep), deep (40-60 cm deep), very deep grave (from 90 cm) and coffin (2 m).

Table 13.3 Listing of insects of forensic importance (after Amendt et al. 2004 and Gennard 2007)

Gennard(additional

Table 13.3 Listing of insects of forensic importance (after Amendt et al. 2004 and Gennard 2007)

Gennard(additional

Amendt

Gennard

species)

Order/family

Important genera

Diptera

Calliphoridae

Calliphora,Chrysomya, Cochliomyia, Lucilia, Phormia

Listed

Drosophilidae

Drosophila

Not mentioned

Ephydridae

Discomyza

Not mentioned

Fanniidae

Fannia

Listed

Heleomyzidae

Heleomyza, Neoleria

Not mentioned

Muscidae

Hydrotaea, Musca, Muscina, Ophyra

Listed

Phoridae

Conicera, Megaselia

Listed

Piophilidae

Piophila, Stearibia

Listed

Sarcophagidae

Liopygia, Sarcophaga

Listed

Sepsidae

Nemopoda, Themira

Listed

Sphaeroceridae

Leptocera

Listed

Stratiomyidae

Hermetia, Sargus

Not mentioned

Trichoceridae

Trichocera

Listed

Coleoptera

Cleridae

Necrobia

Listed

Nitidulidae

Dermestidae

Attagenus, Dermestes

Listed

Carabidae

Geotrupidae

Geotrupes

Listed

Scarabaeidae

Histeridae

Hister, Saprinus

Listed

Trogidae

Silphidae

Necrodes, Nicrophorus, Silpha

Listed

Tenebrionidae

Staphylinidae

Aleochara, Creophilus

Listed

Lepidoptera

Tineidae

Tineola

Hymenoptera

Ichneumonidae

Alysia

Pteromalidae

Nasonia, Muscidifurax

Table 13.4 Examples of insects (and arthropods) of forensic importance in burial environment. Bou: Bourel et al. 2004; Gau: Gaudry et al. 2006; Mot: Motter 1898; Meg l:Megnin 1894 (Ivry) and Meg 2: Megnin 1884 (St Nazaire); Mer: Merritt et al. 2007; Pay: Payne et al. 1968; Smi Smith 1986; Tur: Turner and Wilshire 1999-, Van 1: CMH zone Ex; Van 2: SBS zone Ex (After VanLaerhoven and Anderson 1999)

Table 13.4 Examples of insects (and arthropods) of forensic importance in burial environment. Bou: Bourel et al. 2004; Gau: Gaudry et al. 2006; Mot: Motter 1898; Meg l:Megnin 1894 (Ivry) and Meg 2: Megnin 1884 (St Nazaire); Mer: Merritt et al. 2007; Pay: Payne et al. 1968; Smi Smith 1986; Tur: Turner and Wilshire 1999-, Van 1: CMH zone Ex; Van 2: SBS zone Ex (After VanLaerhoven and Anderson 1999)

Deep

Very deep

Type of grave

<10

cm

Shallow (~

10-30 cm)

(-40-60 cm)

(>90 cm)

Coffin (2 m)

Important

Order/family

genera/author

Lun

Tur

Lun

Vanl

Van2 Rod

Gau Lun Pay

Pay Gau

Bou Mer

Mot Smi Meg

Meg2

Diptera

Calliphoridae

Calliphora, Chrysomya, Cochliomyia, Lucilia, Phonnia

X

X

X

X

X

XXX

Drosophilidae

Drosophila

X

X

X

X

X

X X

X X

X

XXX

X

Ephydridae

Discomyza

X

X

X

X

X

Fanniidae

Fannia

X

X

Heleomyzidae

Heleomyza, Neoleria

Muscidae

Hydrotaea, Musca, Muscina, Ophyra

Phoridae

Conicera, Megaselia

X

X

X

X

X

X

XXX

X X

X X

XXX

X

Piophilidae

Piophila, Stearibia

X

X X

X X

X

Sarcophagidae

Liopygia, Sarcophaga

X

X

X

X

Sepsidae

Nemopoda, Themira

X

Sphaeroceridae

Leptocera

Stratiomyidae

Hennetia, Sargus

Trichoceiidae

Trichocera

Coleoptera

Cleridae

Necrobia

X

X

X

X

X

XXX

X X

X

XXX

X

Dermestidae

Attagenus, Dennestes

X

X

X

X

X X

X

Geotrupidae

Geotrupes

X

X

X

X

X

Histeridae Hister, Saprinus

Histeridae Hister, Saprinus

(continued)

Table 13.4 (continued)

Type of grave

<10 cm

Shallow (-10-30 cm)

Deep (-40-60 cm)

Very deep (>90 cm)

Coffin (2 m)

Order/family

Important genera/author

Lun Tur

Lun Vanl Van2 Rod

Gau Lun Pay

Pay Gau

Bou Mer Mot Smi Meg Meg2

Silphidae Staphylinidae

Necmdes, Nicmphorus,

Silpha Aleocham, Creophilus, Philonthus

Hymenoptera Formicidae

X

X

X

X

Pteromalidae

X

Others

X

X

X

X

Acari

X

X

X X

X

X

Collembola

X

X

X X

X

X

In a shallow grave, the diversity of Arthropods is logically greater, the with presence of different families of Diptera, Coleoptera and Hymenoptera as well as Acari and Collembola. In a shallow grave and within the coffin fauna, Calliphoridae are well represented. In the second medium (coffin), cultural habits may have a direct impact of this observation due to the exposition of the deceased before being placed in a casket. Predominance of Muscidae and Phoridae is obvious after burial. In deep and very deep graves, insect activity is poor, with very few families within each order. Data are rare in deeper graves (>90 cm).

Among Coleoptera, Silphidae, Staphylinidae and Histeridae are well represented in shallow graves, whereas at greater depth and witinin the coffin, occurrence of Staphylinidae is important. In the studies considered it is the only family of Coleoptera collected.

Burial modifies the hierarchy established at the surface, discriminating insects of primary importance and those of secondary importance, because of the lack of the former under the soil surface depending on the depth. Time of death, period of burial, exposition of the dead body or carcass before burial have an impact on the insect composition. Time spent before exhumation is important because it has an impact on the insect collection. Indeed, a long period enables an easier insect colonization.

13.5.4.1 Dipterans Found on Buried Corpses

13.5.4.1.1 Calliphoridae

Calliphoridae, considered a major family of forensic importance, is generally collected from a very shallow grave. Lundt (1964) reported that a layer of soil was sufficient to prevent Calliphoridae colonization (Calliphora and Lucilia). Their presence at a greater depth may indicate that the victim has been exposed prior to being buried. If not, no Calliphoridae specimens colonize remains when the soil layer above the cadaver is superior to 40 cm thick. Thus, estimation of reliable PMI is hardly possible.

13.5.4.1.2 Fannidae

Species belonging to this family prefer a moist habitat. According to Vanlaerhoven and Anderson (1999) such behaviour may explain the presence of immature stages of Fannia canicularis at early stages of decomposition. The same species was identified by Gaudry et al. (2006) at 30 cm depth with F. scalaris. Fannia manicata and F scalaris were identified by Bourel et al. (2004) in coffins.

13.5.4.1.3 Heleomyzidae

Turner and Wiltshire reported that a PMI estimation was based upon a Tephoclamys rufiventris (Heleomyzidae). Heleomyzidae are regularly collected among the population of unburied (Smith 1986) and buried cadaver (Vanlaerhoven and Anderson

1999). Specimens belonging to Heleomyzidae have been collected at 90 cm depth, 1 year after the burial of lamb carcasses (Gaudry et al. 2006). A lack of identification and/or development data on species of this family does not enable it to be associated to insect population of forensic importance.

Such a situation can be compared to the Stratiomyidae (soldier flies) collected by Motter (1898) and other workers (see below).

13.5.4.1.4 Muscidae

Lundt (1964) highlighted the predominance of Muscidae in a shallow grave (2.5 and 10 cm deep) represented by two species: Muscina pabulorum Fallen and Ophyra leucostoma Wiedemann, whose females lay eggs on the soil surface above the buried substrate (flesh). Vanlaerhoven and Anderson (1999) observed a chronological succession pattern on buried carrion bteween Calliphoridae (Calliphora vomitoria) and Muscidae (Hydrotaea sp., Morellia sp. and Ophyra leucostoma) 6 weeks after death, as previously reported by Smith (1986). Muscina and Ophyra were predominant genus in a shallow grave (Gaudry et al. 2006). From very deep graves, the authors collected individuals of Muscina sp. Ophyra capensis was identified by Bourel et al. (2004) in coffins.

13.5.4.1.5 Phoridae

Scuttle flies are described in many experiments of exhumation of bodies. As previously mentioned for Muscidae, this family is the most represented in a burial environment. Some authors (Disney 1994) suggested that some Phoridae collected on buried carrion may play a similar fonction to Calliphoridae in exposed ones.

Lundt (1964) found adults of Metopina sp. and Conicera sp. at a depth of 25-50 cm 4 days after, burial in Germany.

Payne et al. (1968) collected Dohrniphora incisuralis (Loew) and Metopina subarcuata Borgmeier from pig carcasses buried 50-100 cm deep, on the third day and actively feeding on the seventh day.

This family was also present in Coastal Western Hemlock zone and Sub-boreal Spruce (British Columbia). Vanlaerhoven and Anderson (1999) collected in this area specimen of Dohrniphora sp. but only at the adult stage on pig carcass buried 30 cm below the surface. Conicera tibialis Schmitz specimens have been collected at 90 cm depth, 1 year after the burial of lamb carcasses (Gaudry et al. 2006).

Bodies buried may be revealed by the presence of coffin flies, Conicera tibialis, whose presence on the soil surface could indicate the location of a buried body (Leclercq 1999, Gennard 2007). Disney (1994) reported too frequent occurence of this species on buried corpses .

They are generally found at pupal stage on hair of exhumed deceased persons or peal and wool of animal carcasses (Fig. 13.3). Their adults are supposed to be able to move to a significant depth (1 m and more when found in coffins at 2 m deep) through the ground (Disney 1994). Other authors (Colyer 1954a,b ) suggested a 'one-way traffic' from the body to the ground level.

13.5.4.1.6 Piophilidae

Motter collected Piophila casei Linné (named as Sepsidae) among the fauna of many coffins studied. Stearibia nigriceps (Meigen) was collected by Vanlaerhoven and Anderson (1999) but only at the adult stage on pig carcasses (see above).

13.5.4.1.7 Stratiomyidae

Main Stratiomyidae (Hermetiinae, Sarginae) are more opportunistic than necrophagous. That is why they can be classified at first as species of secondary forensic importance. Motter (1898) found specimen of Stratiomyidae in coffins. Hermetia illlucens (Linné) (Stratiomyidae) has been described on buried human remains in the United States and Hawaï (Lord et al. 1994). Studies showed that this species colonizes remains during later stages of decay (drier, post-decayed stages).

13.5.4.2 Coleopterans Found on Buried Corpses: Staphylinidae and Rhizophagidae

Coleoptera are present in every kind of medium: surface, ground, on carrion, vegetation, etc. Many specimens belonging to this order are found on exposed-above ground as well as buried bodies. If the diversity is very important in open-air corpses, Coleoptera are less predominant underground (grave and coffin). Such situations may be partially explained by their trophism. Many of them are not carrion feeders but predators or fungi feeders (see below).

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