Historic Roots and Importance of Mites

In one of the first reports of modern forensic entomology, Brouardel describes the case of a newborn child that was found as a mummified body in January 1878 (Benecke 2001; Brouardel 1879). The time of death was independently estimated based on caterpillars and mites present on the corpse. The caterpillars were studied by Perier and identified as belonging to the genus Aglossa and might have been A. caprealis (Pyralidae, Lepidoptera), also known as murky meal moth, fungus moth, small tabby, or a similar species. The moth would have infested the corpse the summer before. For the mites, Megnin was consulted. The corpse was covered with large quantities of mite feces and exuviae, the skins that are cast during moulting, which produced a brownish layer on top of the body. Large numbers of a single mite species, Tyroglyphus longior, now known as Tyrophagus longior (Acaridae, Astigmata), were present inside the cranium. Megnin estimated that the entire corpse carried about 2.4 million mites, dead or alive. Assuming a generation time of 15 days for the species based on his own observations and life tables for T. mycophagus and assuming every female gave birth to ten female and five male offspring, he calculated back the number of generations that would have been required to account for the number present on the corpse. The mites would have arrived by phoresy some two months after death, when the corpse had lost enough humidity to support the development of the mite colony. The total estimate for the time of death was around 7-8 months before the autopsy (Mégnin 1894). This early report links phoresy, mites and the determination of a post-mortem interval. Since the case of the mummy in 1878, mites have been detected regularly on human and animal remains and noted in many reports. However, often these mites have just been listed as Acari and not used for any forensic deduction. Few studies addressed mites and arthropods other than insects directly (Anderson and Vanlaerhoven 1996; Bourel et al. 1999; Braack 1986; Goff et al. 1986; Goff and Odom 1987; Grassberger and Frank 2004; Hewadikaram and Goff 1991; Hunziker 1919; Leclercq and Vaillant 1992; Leclercq and Verstraeten 1988b; Mégnin 1887, 1889, 1892; Pérez et al. 2005; Richards and Goff 1997; Shalaby et al. 2000; Vance et al. 1995; Yovanovitch 1888). Leclercq and Verstraeten recorded mites for decomposing human remains, Goff for carcasses of domestic cats and Centeno and Perotti for carcasses of domestic pigs (Centeno and Perotti 1999; Goff 1989; Leclercq and Verstraeten 1988a). The following table presents a list of the mite genera which are likely to arrive as phoretics in any of the five stages of decomposition according to Goff (2009) (Table 5.1). A complete catalogue compiling all the phoretic species known to arrive at a corpse carried by forensically

Table 5.1 Occurrence of phoretic mites according to the insect carriers associated with the stages of decomposition. The most common carriers are indicated for each wave or stage of decomposition; when only a few genera are known, the predominant genera are presented otherwise the family is indicated.

1. Initial decay, fresh stage

Main carriers are flies (Calliphoridae, Muscidae, Phoridae and Sciaridae). Most Mesostigmata and Prostigmata are specific to the genera of their hosts.

MESOSTIGMATA

Family Macrochelidae

Macrocheles (phoretic females) Family Uropodidae

Uroboovella Family Trachytidae Uroseius

PROSTIGMATA

Family Pygmephoridae Pediculaster

ASTIGMATA

Family Histiostomatidae

Mostly Myianoetus and Histiostoma Family Acaridae

Sancassania and Acarus

2. Putrefaction, bloated stage

Main new arrivals are carrion beetles (Silphidae).

MESOSTIGMATA

Family Macrochelidae Family Eviphididae

(continued)

Table 5.1 (continued)

Family Uropodidae Uroboovella

ASTIGMATA

Family Histiostomatidae Spinanoetus

3. Black putrefaction, active decay, decay stage

Most representative carriers of this wave are carrion and clown beetles (Silphidae and

Histeridae).

MESOSTIGMATA Family Parasitidae

Parasitus and Poecilochirus

Family Macrochelidae

Several species specific to beetles Family Eviphididae Family Rhodacaridae Family Uropodidae Uroboovella

PROSTIGMATA

Family Pygmephoridae Bakerdania

ASTIGMATA

Family Histiostomatidae

Spinanoetus Family Acaridae

Schwiebea and Sancassania

4. Butyric fermentation, advanced decay, post-decay stage

Expected new carriers arriving at this stage of decomposition are cheese flies (Piophilidae);

some vinegar flies (Drosophilidae), dark-winged fungus gnats and hump-backed flies

(Sciaridae and Phoridae) depending on the degree of fermentation; hide and carcass beetles

(Dermestidae and Trogidae) depending on the level of dryness of tissues.

MESOSTIGMATA Family Parasitidae

Few Poecilochirus are specific on Trogidae Some species on Drosophilidae Family Macrochelidae

Macrocheles and Neopodocinum carried by Trogidae. Macrocheles on Drosophilidae, expected on Piophilidae, Phoridae and Sciaridae as well Family Halolaelapidae

On Sciaridae and Phoridae flies Family Digamasellidae

On Sciaridae Family Ascidae

Hoploseius and Proctolaelaps on Drosophilidae Family Uropodidae

Uroboovella on Dermestidae Family Trachytidae

Uroseius on Phoridae

(continued)

Table 5.1 (continued)

PROSTIGMATA

Family Pygmephoridae

Pediculaster mostly on Trogidae and Sciaridae

ASTIGMATA

Family Histiostomatidae

Rhopalanoethus and Histiostoma, on Trogidae, Sciaridae and Phoridae Family Lardoglyphidae

Mostly Lardoglyphus on Trogidae and Dermestidae Family Acaridae On Trogidae Family Euglycyphagidae

On Trogidae Family Winterschmidtiidae On Trogidae

5. Dry decay, dry decomposition, skeletal stage, remains stage

Main carriers at this stage are moths (Tineidae and Pyralidae) and beetles such as hide, larder or carpet beetles (Dermestidae) or carcass beetles (Trogidae) might arrive to the corpse depending of the level of dryness.

MESOSTIGMATA Family Parasitidae

Few Poecilochirus are specific on Trogidae Some species on Drosophilidae Family Macrochelidae

Macrocheles and Neopodocinum carried by Trogidae. Family Laelapidae

On other moths (Noctuidae) Family Ascidae

Blattisocius on Tineidae and other moths Family Uropodidae

Uroboovella on Dermestidae

PROSTIGMATA

Family Pygmephoridae

Pediculaster mostly on Trogidae Family Cheyletidae

Cheletomorpha on Tineidae

ASTIGMATA

Family Histiostomatidae

Rhopalanoethus and Histiostoma on Trogidae Family Lardoglyphidae

Mostly Lardoglyphus on Trogidae and Dermestidae Family Acaridae

Various genera on Trogidae and Sancassania on moths Family Euglycyphagidae

On Trogidae Family Winterschmidtiidae On Trogidae important scavengers is presented in Perotti and Braig (2009). This table offers just a general guide, because the insects can be different according to region or circumstances of death and the phoretic fauna will change accordingly.

The human follicle mites Demodex folliculorum (Demodicidae, Prostigmata), which are primarily found in the hair follicles of the eyelashes and eyebrows, and D. brevis, which live in sebaceous glands connected to hair follicles, have gained the attention of pathologists during autopsies (Ozdemir et al. 2003). More than a 100 years after mites had first been used in France to establish a post-mortem interval for a homicide case, Lee Goff again used acarological data in a case of a burial on the island of Oahu, Hawai'i (Goff 1991).

The localized distribution patterns of mites led ultimately to a conviction in a murder trail in California. A police officer and another 20 members of a search team got bitten by chiggers of the mite Eutrombicula belkini (Trombiculidae, Prostigmata) when investigating the body of a 24-old woman at a rural location. This mite species was restricted to a very limited area around the crime scene (Prichard et al. 1986; Webb et al. 1983). It normally feeds on lizards and birds and only occasionally of humans (Bennett and Webb 1985). One of the suspects exhibited a similar characteristic biting pattern to the police officer. The extant of inflammation at the bite site of the suspect was used to estimate the time of the original bites. In this case mites put the suspect both at a specific place as well as at a specific time.

The cover of one of the major monographs, Forensic Entomology: the Utility of Arthropods in Legal Investigations, might serve as a final example of how widespread and easily overlooked phoretic mites are in a forensic setting; it shows a carrion beetle and on its right front leg a tiny phoretic parasitiform mite (Byrd and Castner 2001).

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