Indoor Decomposition

According to Mann et al. access for arthropods to the body is the second most important variable after temperature affecting the decomposition of a body (Mann et al. 1990). This should be most pronounced in any kind of concealment, wrapping or relatively well sealed spaces such as containers, cars, car trunks, trucks, or closed kitchen appliances (Anderson 2010). The limiting factor here should be the diameter of the opening such as the 1 cm hole caused by the missing front door handle of the kitchen appliance. Shelter in itself provided by a roof should have little influence on the fauna of the corpse. In a comparison in Argentina, no differences between sheltered and exposed to open sky were found in summer; only in winter, the sheltered pig carcass attracted the secondary screwworm, Cochliomyia macellaria (Calliphoridae), and the rare Phaenicia cluvia (Calliphoridae) in addition to the common bluebottle Calliphora vicina (Calliphoridae) (Centeno et al. 2002). The hypothesis put forward is that the level of endophyly or exophyly of a species should determine the likelihood of its appearance at a decomposing corpse and that the level of concealment that human habitation provides might be of minor importance. It has been found that decomposition generally occurs faster in outdoor environments in comparison to indoor environments. This delay could broaden the range of PMI values if not fully understood.

A recent retrospective of the past 10 years (1998-2008) at the Institute of Forensic Medicine in Frankfurt/Germany shows that 81.9% of the 364 corpses, which were infested by insects, were found indoors. This highlights the need to analyse the insect fauna of indoor situations.

Goff undertook the most explicit comparison of decomposition between indoor and outdoor situations (Goff 1991). Covering a range of 2-21 days post mortem, 14 cases of accidental death, suicide, homicide, and unattended deaths over 8 years were compared to 21 cases retrieved from outdoor locations that were of a corresponding post mortem age. It should be mentioned that all these results suffer from the fact that they were not designed or controlled succession studies but case reports. Therefore a period of e.g. 5-6 days post-mortem might be correct but will depend on the reliability and quality of the general forensic investigation in these cases. At the same time, the example "5-6 days post-mortem" does not rule out the possibility that a certain species might have been there on days 1-4 and still could be there on days 7-10 as well: case data often just represent a small cutout of the whole case history.

One might expect that the numbers of insects are greater in outdoor situations than in indoor locations, but this has not yet been systematically investigated. Under the tropical conditions of Hawai'i, the peak of insect diversity is reached faster indoors, between days 6 and 7, compared to between days 8 and 10 for outside corpses. At later stages, few indoor species contrast to a wide diversity of outdoor species. The indoor carcass fauna was richer in Diptera species while the outdoor fauna was characterised by a higher abundance of Coleoptera species. Table 6.1 serves as an illustration of how often particular species have been reported per number of indoor cases (reports/cases indoors), and how often particular species have been reported from indoor cases and from outdoor cases (indoor/outdoor reports) in the study in Hawai'i.

In Goff's study, insects were not generally associated with decomposing remains discovered indoors above the sixth floor. However, in several cases from temperate regions, insect infestation of human remains have been reported from far taller buildings, e.g., an 11-story apartment building in Gdansk, Poland, and the 18th floor of an apartment complex in Canada (Anderson 2010; Piatkowski 1991).

In most outdoor situations blow flies (Calliphoridae) will dominate the first weeks of decomposition. The large numbers of eggs laid by blow flies will obscure any larva of flesh flies (Sarcophagidae) present. Nuorteva describes blow flies in four indoor cases in Helsinki (Nuorteva et al. 1967). However, in indoor cases it is

Table 6.1 Examples of species associated with human remains found indoors in Hawai'i

Indoor/

Reports/cases outdoor

Table 6.1 Examples of species associated with human remains found indoors in Hawai'i

Indoor/

Reports/cases outdoor

Dayspostmortem

Species

Family

indoors

reports

(hairy maggot blow fly)

Calliphoridae

4/6

4/20

(oriental latrine fly)

3/3

3/14

4,6

Sarcophaga (Boettcherisca) peregrina (flesh fly)

Sarcophagidae

3/4

3/3

5,6,14-21

S. (Bercaea) haemorrhoidalis (red-tailed flesh fly)

4/9

4/0

(chicken dung fly)

Fanniidae

1/3

1/0

chalcogaster (grave fly)

Muscidae

1/3

1/0

6,7

Stomoxys calcitrans (stable fly)

Muscidae

3/4

3/0

6,7

Dermestes maculates (hide beetle)

Dermestidae

2/4

2/11

7,8

Musca domestica (house fly)

Muscidae

2/2

2/1

14-21

Megaselia scalaris (scuttle fly)

Phoridae

5/5

5/0

more likely that flesh flies might prevail. The diversity of flies (Diptera) that can be collected from a flat even in a temperate zone is overwhelming. Schumann collected 2,148 flies belonging to 150 species and 46 families in a flat in the outskirts of Berlin between April and October. Fannia canicularis was the most frequent species with 726 specimens, followed by Drosophila melanogaster, Culex pipiens, Lucilia (Phaenicia) sericata, Sarcophaga carnaria, Calliphora vicina, Muscina stabulans and F manicata, accounting for 55% of the caught flies (Schumann 1990). This study gives again an indication for a possible bias: while most of our knowledge about species diversity in outdoor situations is based on many succession studies with pig cadavers and other carcasses or baits, our knowledge about indoor diversity relies mainly on real cases, which gives just a limited insight in the whole process and time scale of decomposition and insect colonisation. Moreover, one should differentiate strictly between adult and immature stages. In a recent study comparing the colonisation of two pig cadavers placed indoors and outdoors at the same period of the year, we found indeed a higher diversity regarding the adult stages on the pig placed outdoors, but no differences occurred when analysing the numbers of species which colonised the cadavers (J Amendt et al. unpublished). This again illustrates the need for more indoor studies.

Table 6.2 gives a geographically more widespread representation of insect species found on indoor remains. The table limits itself to examples of human cases. Controlled studies of the indoor decomposition of pigs are rare; a recent example is the comparison of indoor and outdoor decomposition in Parma, Italy (Leccese 2004), but this study just deals with small baits (56-90 g pieces of pork meat), definitely not comparable with a human cadaver.

Comparison between summer and winter in the insect fauna on human corpses from 117 domestic cases around Hamburg, Germany, found Calliphora vicina and scuttle flies as all-year species, C. vomitoria, Muscina stabulans, and Dermestes species as spring and autumn species, whereas Lucilia sericata, Phormia regina, and Sarcophaga species as typical summer species (Schroeder et al. 2003).

None of the listed insect species can be considered as exclusively indoors. The various levels of endophily exhibited by insect species will always remain just a bias towards one or the other environment. This bias is expected to change between geographic regions.

Insects may be attracted not by a cadaver, but will infest it secondarily. Some flies such as the false stable fly, Muscina stabulans, and the lesser house fly, Fannia canicularis, are drawn by a wide range of decaying organic matter and are commonly found in human quarters. These flies, for example, are much more attracted to human feces than to the corpse itself. This has led to the use of these flies as an indication for possible neglect (Benecke and Lessig 2001). The oriental latrine fly, Chrysomya megacephala, is equally attracted to feces and can lead to errors in estimates of the postmortem interval in similar cases of neglect (Goff et al. 1991). Similarly, Anderson suggests that the presence of normal household garbage might have been the determining factor for the attraction of several species in her study (Anderson 2010). Additionally, keeping pets indoors could be attractive for these insects, especially in summer.

Table 6.2 Examples of insect species reported from indoor remains

Species

Family

Indoor prevalence Place

Calliphora vicina

Diptera

Calliphoridae Occasional

C. vomitoria

Protophormia terraenovae Chrysomya rufifacies C. megacephala Lucilla(=Phaenicia)

sericata Phaenicia regina

Drosophila spp.

Fannia spp. F. cannicularis F. pusio

Musca domestica Muscina stabulans Hydrotaea spp. H. (=Ophyra) capensis H. (=Ophyra)

chalcogaster Stomoxys calcitrans Synthesiomyia nudiseta Megaselia abdita M. scalaris Piophila spp. Piophila casei Sarcophaga spp. S. (Bercaea)

haemorrhoidalis S. (Boettcherisca)

peregrina Thanatophilus lapponicus

Leptocera caenosa

Occasional Occasional Occasional Common

Common

Drosophilidae Fanniidae

Muscidae

Common

In- and outdoors

Phoridae

Common Piophilidae In- and outdoors

Sarcophagidae

Silphidae Sphaeroceridae

Common Equal

In- and outdoors

Auckland, Belgium, Br. Columbia1,2, Cieza, Hamburg, Helsinki, USA1,2 Hamburg, Leipzig Br. Columbial Oahu Oahu

Auckland, Br. Columbial,

Gdansk, Hamburg, USA1 Br. Columbial, Hamburg,

USA1 Hamburg Canada

Canada, Hamburg Gdansk, Leipzig Oahu Oahu

Gdansk, Hamburg, Leipzig

Br. Columbial

Eraclea

Oahu

Oahu USA2 USA1 Oahu

Br. Columbial France, Victoria Hamburg Oahu

Oahu

Br. Columbial

Canada

Englandl

Tachinaephagus zealandicus Nasonia vitripennis

Hymenoptera

Encyrtidae

Pteromalidae

Eraclea

Eraclea, Hamburg

Necrophilus hydrophiloides

Coleoptera

Agyrtidae

In- and outdoors

Br. Columbia!

(continued)

Table 6.2 (continued)

Species

Family

Indoor prevalence

Place

Necrobia rufipes N. violacea

Cleridae Dermestidae

Eraclea

Canada

Dermestes lardarius

Denmark, USA2

D. haemorrhoidalis

Denmark

D. maculates

Occasional

Eraclea, Germany, Oahu

Hister cadaverinus

Histeridae

Hamburg

Hofmannophila (=Borkhausenia) pseudospretella

Lepidoptera

Oecophoridae

England2

Auckland, New Zealand (Smeeton et al. 1984) Belgium (Leclerq 1969)

British Columbia, Canada 1 (Anderson 1995), 2 (Anderson 2010) Canada (Anderson and Cervenka 2002) Cieza, Murcia, Spain (Arnaldos et al. 2005) Denmark (Voigt 1965)

England 1 (Erzinglioglu 1985), 2 (Forbes 1942)

Eraclea, Venice, Italy (Turchetto and Vanin 2004)

France (Megnin 1894)

Gdansk, Poland (Piatkowski 1991)

Germany (Schroeder et al. 2002)

Hamburg, Germany (Schröder et al. 2001)

Helsinki, Finland (Nuorteva et al. 1967)

near Leipzig, Germany (Benecke and Lessig 2001)

Oahu, Hawai'i (Goff 1991)

USA 1 (Greenberg and Kunich 2005), 2 (Lord 1990) Victoria, Australia (Archer et al. 2005)

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