1. Identification of Arthropod Species on Decomposing
Sus scrofa in Florida
Jonathan Troiano1, Ryan Ebanks2, and Evelyn Frazier3,
Departments of Psychology1, Anthropology2, and Biological Sciences3, Florida Atlantic University
Carrion decomposition has been shown to be accelerated in South
Florida. This accelerated rate has been attributed to environmental
factors such as increased sun exposure, high humidity, heat, and
arthropod species present in the environment. The goal of this study
was to document the arthropod species consuming carrion. Four
Sus scrofa carcasses were caged separately in sites exposed to direct
sunlight in August, at Jonathan Dickinson State Park (JDSP). Insect
eggs and larvae were then collected utilizing aseptic techniques, and
reared in the laboratory. Once matured, the adult flies obtained from the
rearing chamber were euthanized and pinned for identification. At
current, pinned arthropods have been sent to a taxonomist and are
awaiting identification.
Abstract
Various factors1 (fig. 1) such as the arthropods that colonize a carcass,
contribute to decomposition of an organism. The developmental
patterns of those arthropod species that colonize a fresh carcass are
known to be predictable. Given the nature of their developmental
patterns and knowledge thereof, this information can be used as an
inferential tool in the forensic sciences and criminal investigation to
calculate the Postmortem Interval. Proper identification of the colonizing
arthropods will help to more accurately determine the Postmortem
Interval (PMI). The ability to calculate a more precise PMI will aid in
studies of forensic science and criminal investigation. Among the
studies previously conducted that examine these patterns, there exists
a deficit of research conducted in the neotropical environment of South
Florida.
Introduction
Materials & Methods
Each Sus scrofa carcass was placed in a wire mesh cage (fig. 2) designed to permit arthropod access
but deny vertebrate access. Each cage was then placed in a sunlit environment, where the
decomposition process would begin. Over the course of the experiment, each cage was checked daily.
On day 2 the insect larvae were then collected, housed in a container with beef liver for sustenance
whilst in transit to the laboratory, where they were then transferred into their corresponding chamber
within the terrarium (fig. 6).
Preliminary Results
Initial results demonstrated a decomposition rate far more dramatic
than anticipated2. Carrion colonized by arthropods demonstrated
skeletonization (fig. 4D) but not total dessication within 10 days (the
first 24 hours were counted as ‘day 0’) leaving behind only bone.
Contrary to our hypothesis, Dermestidae were not present on the
carrion, only organisms of order Diptera. Collected fly species are
awaiting identification of species.
Acknowledgements
FAU Office of Undergraduate Research & Inquiry (OURI)
FAU terrestrial ecology laboratory
Jonathan Dickinson State Park (JDSP)
Dr. Jason H. Byrd
The purpose of our study was to examine the following questions:
• Which arthropod species would inhabit the carcass?
• How much time would elapse until complete desiccation?
• What role would arthropod species have in the
decomposition of the carcass? Would they be a
significant player in the process of decomposition? A
minor factor? Something else entirely?
Objectives
Fig. 2: Cage for housing the Sus scrofa carcass
Upon arrival to the laboratory, larvae remained in the
containers with liver and reared in separate chambers of a
partitioned terrarium with a mixture of soil and vermiculite.
Larvae were reared in a container with beef liver for nutrition,
and moved to the substrate if observed attempting to escape
the container and burrow to begin pupation. Following
pupation, the adult fly would emerge from the pupa, restricted
to its rearing chamber (cages 5-8). Once all insects had
matured and expired, they were removed from their respective
chambers and stored in a container which would then be stored
cold, with or without an 80% etOH solution (standard=70-95%).
LABORATORYFIELD
EGG LARVA PUPA ADULT
Fig. 5: Typical developmental pattern of the fly. Larvae were collected from the carcass and then brought to the laboratory for rearing in the terrarium (fig. 6).
Fig 6: Insect rearing terrarium
Fig. 4: Intervals of carrion decomposition.
SOIL pH
TEMPERATURE
& HUMIDITY
INSECT
COLONIZATION
SOIL MICROBE
COMPOSITION
DAILY RAINFALL
Fig. 1: Factors that contribute to decomposition. This focus of this
project was to investigate the factor of insect colonization.
TIGHT SHOT
OF ONE FLY,
PLUS CAPTION
TIGHT SHOT
OF ONE FLY,
PLUS CAPTION
TIGHT SHOT
OF ONE FLY,
PLUS CAPTION
TIGHT SHOT
OF ONE FLY,
PLUS CAPTION
TIGHT SHOT
OF ONE FLY,
PLUS CAPTION
TIGHT SHOT
OF ONE FLY,
PLUS CAPTION
TIGHT SHOT
OF ONE FLY,
PLUS CAPTION
TIGHT SHOT
OF ONE FLY,
PLUS CAPTION
Discussion
It was anticipated that dermestids would be present during
decomposition, but due to the accelerated speed at which
decomposition occurred, desiccation was completed before the
anticipated arrival of dermestids. Thus, the assumption is that the
reason no beetles were present was due to the complete desiccation of
the body prior to the anticipated arrival of dermestids. As well, the
accelerated rate of decomposition that occurred is suspected to be due
in part to the elevated humidity, temperature, and sun exposure in the
South Florida environment. It should also be noted that, while it is in
part the focus of another facet of this project, the microbial composition
of the soil and the species of colonizing arthropods were affected by
the acidity of the soil3. As was not a pertinent variable of interest in this
experiment, it should be noted that larvae collected from the field (high
temperatures) were then reared in a laboratory environment (lower
temperatures and humidity). Thus, this variable was not controlled for in
this experiment, and could serve as a point of interest for further study.
Identification of arthropod species and carrion decomposition, not
arthropod development, were the focus of this project.
Fig 3: JDSP (A) and detail view of cage locations (B).
References
1. Frankenberger, W.T. and Arshad, M.,1995. Phytohormones in Soils: Microbial Production and
Function. Marcel Dekker Inc., New York, USA., ISBN: 0824794427.
2. Galloway, A., Birkby W.H., Jones A.M., Henry T.E., Parks B.O.,1989. Decay Rates of Human
Remains in an Arid Environment. Journal of Forensic Sciences 34(3): 607–16.
3. Boer, Folman, Summerbell and Boddy 2005:797)
https://entomology.cals.cornell.edu/news-events/news http://entnemdept.ufl.edu/creatures/livestock/flies/lucilia_sericata07.
jpg
http://entnemdept.ufl.edu/creatures/livestock/flies/lucilia_sericata07.
jpg
~24 hr ~130 hr ~140 hr
http://www.diptera.info/forum/viewthread.php?thread_id=27934
Fig X: Decomposition rate of carrion in temperate climate (upper and lower limit), compared with this experiment
and a previous experiment.
