Investigative Study: Insect Bug Faunal Development on Pork Carrion

This report presents an investigation into the insect faunal succession on pork carrion in Wisconsin, USA. The study identified four decomposition stages: fresh, bloated, decay, and dry, distinguished by the carrion's condition and insect species present. High species diversity was observed in the fresh stage, with eighteen species from three orders (Diptera, Coleoptera, and Hymenoptera) and ten families. The study found Diptera species like Calliphoridae, Sarcophagidae, and Muscidae, and several families of Coleoptera. The decomposition process took 12 days, with the fresh stage lasting 48 hours, followed by bloating, decay, and a dry stage. Insect succession involved Diptera, Coleoptera, and Hymenoptera, with Diptera being the most prevalent. The findings are relevant to forensic entomology, aiding in post-mortem interval estimation, and the study highlights the importance of understanding insect behavior and succession patterns in carrion decomposition for forensic investigations.

An investigative study on Insect Bug faunal development on Pork Carrion in
Wisconsin state
Name
Forensic Documentation
Semester
Year
Wednesday/Monday
Tutor’s Name
Date

An investigative study on Insect Bug faunal development on Pork Carrion in
Wisconsin state
Abstract
An investigation of the faunal succession of pork carrion was established in
Wisconsin state, USA. In this process, four decomposition stages were established entailing;
fresh, bloated, decay and dry stages. The stages were differentiated through the species
abundance from the pork and the condition of the carrion in terms of hydration integration,
flaccid nature and desiccation aspects. The results demonstrated that high species were found
in the fresh stage, with a total of eighteen species among three orders and ten families.
Calliphoridae species Sarcophagidae, three of Muscidae were noted in the pork carrion.
Further five families of the Coleopteran families were observed in the pork.
Keywords; Coleoptera, decomposition, Diptera, forensic entomology, faunal
succession
Name: 2

Introduction
Forensic entomology entails the study of insects linked to human dead bodies in an
aim to determine time duration after death or during an assessment of post mortem interval
(Hall, 2011). The underlying mechanisms entail the interaction of insects belonging to
arthropods in a legal process. In determining the estimation of the post mortem interval,
species of dipteral and coleopteran have to be known. In this avenue, the insects can
galvanise the cadavers in a systematic sequence referred to as insect succession. Forensic
entomology entailing medico-legal entomology is essential in estimating the rates of the
interval between death and corpse discovery (Byrd & Tomberlin, 2019). Another avenue of
application entails whether corpses has been moved from the crime scene. Application of
insects and the general arthropods class in forensic entomology is essential in three avenues;
first, the decomposition of the corpse has shown to change in succession during the
modification of cadaver, secondly, the corpse fauna is often ignored during assessment f the
corpse at the death scene. Further, it is noted that arthropods feeders on carrion often form a
distinct succession linked with various stages of decay (Barrios & Wolff, 2011).
Animals have bacteria in their skin and the GI tract. Some of these bacteria are
beneficial while other harmful such as the salmonella, but the animals harbouring them are
not affected. Animals confined in a less clean environment are prone to bad bacteria which
often proliferate easily, the brain and muscles of animals are often sterile, during the
slaughter process, and meats are contaminated with bacteria from the outer surface and
persons handling the meat or the environmental exposure. Further contamination often occur
hence the processing stages are too fast to allow sanitation practices, presence of bacteria on
meat allows it to multiply (Gill, 2005).
Name: 3

Currently in order to reduce contamination of these meats, the federal government
requires food processes to initiate and create safety inspection procedures referred to as
HACCP being implemented in meat and poultry plants.
Having adequate knowledge and skills on aspects of developmental rates, habits the
distribution aspects, morphology and taxonomy of these species are essential in determining
the Post Mortem Interval (Byrd & Castner, 2001). Thus in this view, the key objective of this
task is to assess insects bug succession in decomposition stages and identification of insect
succession trends in pork carrion. This study will be essential in understanding the biology,
ecology and carrion pattern of insect bugs in pig meat.
Materials and Methodology
In order to study the insect succession and decomposition stages, the experiment was
conducted in Wisconsin state, USA. The laboratory experiment was carried out during the
autumn period, which often marks the transition from summer to the winter period, with long
nights and short days fluctuating the environmental temperature. One of the fundamental
features of this climate entails shedding of leaves from deciduous trees. The normal annual
rainfall at the site is about 700 mm. The soil characteristics entail loam sandy soil with pH
levels of 7.8 and 8.5. Sus scrofa Linnaeus species of the pig was used in this study, various
studies have demonstrated that this species has a high level of decomposition which is similar
to human decomposition. The truck region of the pig was used in this study with a weight of
5 kg able to facilitated close observation of the insects and bugs. The pork meat was placed in
the floor dimension of 3x3x3 ft so as to protect any scavengers.
Name: 4

Sampling
Sampling was processed tow times a day in the morning and evening. Flying insects
sampling of insects –Diptera was undertaken with the use of aerial swipe net. The flies were
obtained using hand sweeping net on the pork carrion and collected to killing jar having ethyl
acetate vapours. The beetles were collected using forceps. The tiny insects such as ants were
obtained using fine brush having alcohol. the decomposed pork was then lifted on fauna
sample. The soil analysis below the pork was assessed for post-feeding pupae and larvae. The
insects were collected using vials with 70% ethanol and labelled accurately indicating date
and time of observation. The collected samples were viewed and assessed using Zoom
Stereomicroscope and identified by running the keys for Muscidae, Calliphoridae,
Sarcophagidae and Coleoptera as per their morphological aspects (Sukontason et al., 2004).
The decomposition variation was assessed based on the humidity and temperature while
ambient air temperature assessed using Thermo hygrometer.
The immature stages of the larvae were collected from the pork using forceps and
brought t lab for cultivation. The larva was placed in the sawdust, the developmental stages
were observed until adulthood stage. After full development the flies were identified using
running based on their morphological characteristics.
Statistical analyses entail an assessment of various parameters such as the relative
abundance, frequency of dominance and appearance variation during the different stages of
decomposition with ANOVA test of the variant being applied.
Results and Discussion
The pork took 12 days to completely decompose; the stages entailed in the
decomposition were fresh, bloated, decay and dry decay process. In the fresh stage, it starts at
Name: 5

the death occurrence and continues to the beginning of the bloated stage. In this study, the
fresh stage remains active for a period of 48 hours, autolysis is occurring at this stage
entailing breakdown of complex proteins and carbohydrates into simpler compounds (Van
Doorn, 2011) as observed in figure 1. During the stage of bloating, the initial sign entails
inflation, swelling and pork putrefaction, signalling onset of the decomposition process, the
inflation process starts with intestinal gases leading to the production of anaerobic bacteria
(Stadler, 2013). Further, there is the occurrence of odour at this stage, the fluids start dripping
from the body, with intense maggot activity leading to putrefaction. The further internal
temperature started to increase at this stage with elapse of 96 hours.
Figure 1 Decomposition stages of the pork carrion
During the decay stage, the pork is deflated through the release of gases such as NH3,
CO2, NO2 and H2S. Further observation of post-feeding of maggots beneath the soil was
observed. The pork displayed cracked places demonstrating feeding activity. At this stage,
90% of the biomass was consumed by the maggots.
Name: 6

During the dry stage, only dry skin and vertebral column bones remained. Studies
have shown that this stage can be active beyond the presence of the carrion fauna. The end-
stage is thus difficult to ascertain and lack of any specific occurrence in the stage. Studies
further have demonstrated that each stage of decay comprises of specific species of insects
which is dependent on the physical and chemical properties which are dependent on the
environmental and decomposition factors (Wallinger et al., 2013).
The succession of the insects in this study demonstrates the presence of Diptera,
Coleoptera and Hymenoptera species with the Diptera being the major one. Close to 180
dipteran species were obtained in the C. megacephala, Sarcophaga sp., Musca domestica and
Anthomyia species being prevalent.
In dipteral, nine species belonging to this order belong to four families were
observed in the pro carrion, these species are Chrysomya megacephala (Fabricius),
Chrysomya rufifacies, Lucilia sericata, Lucilia cuprina, Sarcophaga sp., Musca domestica
(Linnaeus), Musca sorbents Musca autumnalis andAnthomyia sp. from families
Calliphoridae, Sarcophagidae, Muscidae and Anthomyidae. Further immature stages of seven
species were observed such as Chrysomya megacephala, Chrysomya rufifacies, Lucilia
sericata, Lucilia cuprina, Sarcophagasp., Musca domestica and Anthomyia sp. Pupae
presence of Chrysomya megacephala and Chrysomya rufifacies were present in the bloated
stage and active decay stage.
Further, some of the flies’ species were observed in the carrion insects and are
essential. The habit differently but are attracted to the carrion by the carrion insects. In this
fresh fly, house fly and blow fly are having forensic impotence. They are abundant in flesh
and are key in determining post mortem index.
Name: 7

Studies have demonstrated that Chrysominae and Calliphorinae are highly present in
the earlier stages. C. Megacephala is often frequent and is attracted to the carrion and is
influenced by foods and sweets which act as mechanical vectors (Sabanoğlu & Sert, 2010).C.
rufifacies have been employed in the maggot therapy on osteomyelitis (Synonymous author
n.d).C. rufifacies is a fundamental aspect of forensics assessments due to its ability to be
predicted through development time, low larval length and lowered levels of regional
variation. These flies feed on fresh and fluid seeping from pork displaying macrophage
nature. These flies were observed during the initial stages of the decomposition, its action
entails colonization of the pork in the first 48 hours. The Sarcophagids are primary invaders
of carcasses and has been shown to have faunal succession in pigs (Horenstein, Rosso &
García, 2012). Further Muscidae family was noted to the present in the pork. The species
present were Musca autumnalis, Musca sorbents, and Musca domestic. Muscid flies are the
first flies to be observed at the carrion with the most abundant after the Calliphoridae (Anton
et al., 2011). Studies have demonstrated that Hydrotaea rostrata (Muscidae) primary
colonizers are present in pigs (Eberhardt & Douglas 2008). Further Muscid flies have been
shown to the predominant species in the pig carrion while a study by Battan et al. (2012),
have shown forensic impotence of Musca domestica on the pig carrion Linnaeus.
In the Coleoptera family seven species were present in the decomposing pork carrion
these entailed Euspiltus assimilis, Saprinus sp., Dermestes maculatus, Gonocephalum
patruele , Typhaea stercorea, Philonthus longicornis, Phileurus truncates. Histeridae,
Dermestidiae, Tenebrionidae, Staphylinidae and Nitidulidae are part of the beetle family
visible in the pork carion. The Saprinus sp.,Dermestes maculatus,Phileurus truncates was the
dominant beetle species are present in the initial stages while the Euspilotus assimilis,
Saprinus sp. and Dermestes maculates were abundant in the bloating stage (Horenstein,
Rosso & García, 2012).
Name: 8

Beetles of the Histeridae and Dermestidae are predominant during the early stages of
decomposition and have the ability to feed on the flesh and the most skin while the
tenebrionids are prevalent in the later stages. Different families have been observed in the
different stages of decomposition such as ilphidae, Histeridae, Staphylinidae were observed
in the bloating stage while in the decay stage included families Silphidae, Histeridae while in
dry stage families Cleridae, Dermestidae, and Trogidae were present. In post decay stage,
studies have shown that beetles are common and play a key role in the decomposition process
with no decomposition order. Carrion beetles have been shown to avoid competition and tend
to appear in the dry stages as compared to wet stages to avoid competing with blow flies. Dry
corpse has been demonstrated to attract beetle fauna. The fundamental type of families
appearing in the earlier stages entails Dermestidae and Tenebrionidae (Goddard, 2012).
In the Hymenoptera, two ants species was found notches graeffei and Camponotus
compressus belonging to the family of Formicidae were present in the initial stages of the
decomposing. Anochetus graeffei were observed during the bloating, advanced and decaying
stage while Camponotus compressus species were found in the fresh and bloating stages.
Ants feeding on the maggots and eggs of fly delayed the clearance process of soft tissue.
These species fed on the outer skin showing dominance in the decay stage.
In this study the mean values of the different insect's orders were established, this
entailed Diptera, Coleoptera and Hymenoptera with evaluation in each stage being
undertaken as observed in table 1 below demonstrating the variance in different insect orders
during the decomposition stages. A sum total of 157 species of Dipterans were obtained from
the decomposed pork with high abundance being at the fresh stage while low abundance level
was obtained in the advanced and decaying stage. In the Coleoptera stage, 28 species were
obtained with abundance being beetles species at fresh and bloated stages, in the
Hymenoptera, 12 species were obtained. The standard error demonstrated variation in the
Name: 9

fresh and bloated stages while the species in the bloating and active stage demonstrated same
value levels. further, a huge error difference was observed between the fresh and active stage.
Table 1 One way ANOVA analysis
The relative abundance of the total species was showed to from C. Megacephala
with 36.91% while Anthomyiia sp showed a relative frequency of 14.28%. In the order
coleopteran Saprinus sp was the abundant species having 4.20% as observed in table 2 below;
Table 2 Relative abundance of species
Name: 10

Temperature and humidity have been shown to have an effect on the decomposition
rates. High temperature increases the rate of decomposition while lower temperature lowers
these rates. The fly larvae are linked to remains of the decomposing and developed at a rate
which is similar to that of the ambient surrounding. Insects are poikilothermic which have
been demonstrated to slow down during low-temperature levels (Compobasso et al., 2001).
With a decrease in the insects’ activity, the decomposition is lowered at low temperature. In
the study a temperature level estimation was shown at 29 ± 4ºC and 67 ± 4% as observed in
figure 2 and 3 below;
Figure 3 Humidity variation in the experiment period
Conclusion
This study offers a basic assessment and data regarding the colonization of insects
during various decomposition stages. This is a crucial step in identifying bugs and insects
which are linked to human corpse decomposition process which is a critical avenue in the
field of entomology which is essential in solving crimes and connecting trends of deaths. In
this model experiment, it is evidenced that the C. megacephala (Diptera) and Saprinus sp.
(Coleoptera) are the common species prevalent during the decomposition and decaying
process as observed in the pork carrion.
Name: 11
Figure 2 Temperature Variation in the
study

References
Anderson, G. S., Cervenka, V. J., Haglund, W., & Sorg, M. (2002). Insects associated with
the body: their use and analyses. Advances in forensic taphonomy: method, theory,
and archaeological perspectives, 173200.
Anton, E., Niederegger, S., & Beutel, R. G. (2011). Beetles and flies collected on pig carrion
in an experimental setting in Thuringia and their forensic implications. Medical and
Veterinary Entomology, 25(4), 353-364.
Barrios, M., & Wolff, M. (2011). Initial study of arthropods succession and pig carrion
decomposition in two freshwater ecosystems in the Colombian Andes. Forensic
Science International, 212(1-3), 164-172.
Byrd, J. H., & Castner, J. L. (2001). Insects of forensic importance. Forensic entomology:
The utility of arthropods in legal investigations, 43-79.
Byrd, J. H., & Tomberlin, J. K. (Eds.). (2019). Forensic entomology: the utility of arthropods
in legal investigations. CRC press.
Campobasso, C. P., Di Vella, G., & Introna, F. (2001). Factors affecting decomposition and
Diptera colonization. Forensic science international, 120(1-2), 18-27.
Eberhardt, T. L., & Elliot, D. A. (2008). A preliminary investigation of insect colonisation
and succession on remains in New Zealand. Forensic Science International, 176(2-
3), 217-223.
Gill, G. J. (2005). Decomposition and arthropod succession on above ground pig carrion in
rural Manitoba.
Name: 12