Transcript forensic_entomology_teacher_presentation

Forensic Entomology
Overview of
presentation:
1. What is forensic
entomology?
2. Medicocriminal
entomology.
3. How long has a particular
individual been dead?
A. Developmental times
of insects.
B. Insect succession.
4. Description of a project
being conducted at ASU.
What is Forensic Entomology?
The study of insects and other arthropods to legal issues.
Broad field.
It can be divided in three subfields:
1. Urban Forensic Entomology
2. Stored-product Forensic Entomology
3. Medicocriminal Entomology
Medicocriminal entomology usually involves:
1.
The intrigue surrounding human or animal death.
2. The decay process.
3.
Detective work necessary to bring perpetrators to trial.
A typical question posed to a medicocriminal entomologist:
How long has a particular individual been dead?
Estimates of time a decedent has been dead “PMI” =
Postmortem Interval.
Involves application of the temperature-dependent
development of insects.
Insect Succession
One important biological phenomenon that occurs on
cadavers are a succession of organisms that thrive
on the different parts.
1. Flies lay eggs usually within the first 24 hours
2. Predatory rove beetles or parasites that feed on
maggots will have to wait until the blow flies arrive
and lay their eggs.
3. Beetles that specialize on bone, will have to wait
until bone is exposed.
The succession on cadavers happens in a fairly
predictable sequence and can be used in estimating
time of death if the body has been lying around for
some time.
Show:
YouTube: Maggots feast on animal carcass
ORDER DIPTERA
Commonly called flies.
Over 86,000 known species, over 16,000 occur in North America.
One of the largest insect orders.
Found in almost every habitat.
Complete metamorphosis.
Body characteristics:
One pair of wings.
Second pair of wings reduced to knob-like
organs called HALTERES (used to
stabilize flight).
Compound eyes.
Mouthparts vary (sponging, piercing,
cutting- sponging)
Flies associated with carrion have SPONGING mouthparts
Pseudotrachea
The Life Cycle of a Fly
Adults
Exact time
depends on
temperature
and moisture
Larvae
3 instars
Prepupal stage
Pupae
Pupae are cylindrical.
Posterior spiracles also present
(used for identification).
Developmental Data on Blow Flies and Flesh Flies
27°C and 50% humidity
Species
Egg
(Hrs)
1st
instar
(Hrs)
2nd
instar
(Hrs)
3rd
instar
(Hrs)
Prepupa
(Hrs)
Pupa
(Days)
Sarcophaga cooley
----------
24
18
48
96
16
S. shermani
----------
22
16
48
104
14
S. bullata
----------
26
18
54
112
17
Phormia regina
16
18
11
36
84
11
Protophormia terranovae
15
17
11
34
80
11
Lucilia sericata
18
20
12
40
90
12
Eucalliphora lilaea
22
22
14
36
92
13
Cynomyopsis cadaverina
19
20
16
72
96
18
Calliphora vomitoria
26
24
48
60
360
23
C. vicina
24
24
20
48
128
18
C. terranovae
25
28
22
44
144
20
Blow Flies (Family Calliphoridae)
Extremely large family of medium-sized flies.
~1,000 spp., found worldwide.
Along withYouTube:
sarcophagid
and muscid
flies,
the most
important
“Maggots
feast on
animal
carcass”
species that provide information relating to accurate estimation of
the postmortem interval.
Attracted to carrion and excrement, with some exploiting open
wounds.
First to arrive at a crime scene.
Black Scavenger Flies (Family Sepsidae)
Worldwide in distribution with
at least 240 spp.
Adults are small, shining black,
purple, or red flies.
No more than 3.5 mm in length.
Head is noticeably rounded.
There is a constriction at the
base of the abdomen.
Behavior: Flick their wings
outward as they walk (“waggle
flies”).
Beetles (Order Coleoptera)
Largest order containing a third
of all known insects (300,000
spp.).
30,000 spp. found in N. America.
Complete metamorphosis (egg,
larvae, pupae, adult).
Characteristics:
ELYTRA – Front wings hard;
covers and protects the hind
wings (membranous) that are
used for flight.
Adults: Chewing mouthparts
Most can fly
Feeding habits vary:
Predacious,
Scavengers,
Herbivores
Carrion Beetles, Family Silphidae
Large family, nearly worldwide in
distribution.
1,500 spp. worldwide; 46 spp. in
N. America.
Medium sized to large beetles
(10 to 35 mm).
Antennae are clubbed.
Elytra are often short and leave
several abdominal segments
exposed.
Body is usually black, marked
with orange, yellow or red
patches.
Larvae vary in size and shape.
Generally 15 to 30 mm long.
Most are flattened.
All larvae are capable of mobility.
Clown Beetles, Family Histeridae
Large family with over
3,000 spp.
500 spp. in North America.
Small, seldom larger than
10 mm in length.
Round bodies and very
shiny.
Elytra are short and
squared at the apex.
Last two abdominal
segments are exposed.
Antennae: Elbowed and
clubbed.
Clown beetles are very
common on carrion and
excrement (found on fungi
and decaying vegetable
matter).
On a carcass, tend to be
concealed in the soil
underneath the body during
the daylight hours.
Most active at night.
Both adults and larvae are
predacious feeding on
maggots, fly pupae and
dermestid larvae.
When collected, must be
separated from other insects.
Skin Beetles, Leather Beetles, Hide
Beetles, Carpet Beetles & Larder
Beetles, Family Dermestidae
Given their names according to
their food preferences.
Worldwide in distribution with
over 500 spp.
123 spp. found throughout North
America.
Small beetles ranging from 2 to
12 mm in length.
Oval in shape, covered with
scales (many colorful patterns).
Feed on various types of dried
animal tissue.
Larvae:
Range from 5 to 15 mm
Usually covered with long tufts of dense hair
Pupa
Adults
Larva
Approximate duration of each stage of decomposition (in days)
of pig carrion in sunny and shaded areas.
Advanced
Decay
Decay
Sun
Shade
Bloat
Fresh
0
2
4
6
8
10 12 14 16 18 20
22
Time Since Death (Days)
24
340
Insect Succession During One Year
Days
Time
Blow fly larvae
Rove beetle adults
Hister beetles adults
Parasitic wasps
Rove beetle larvae
Hister beetle larvae
Dermestid adults
Dermestid larvae
1 2 3 4 5 6 7 8 9 10 11 12 13 14 16 18 20 22 28 3-6 mons. 6-9 mons. 9-12 mons
Occurrence Matrix
Family
Genus/Species
Calliphoridae
Sarcophagidae
Drosophilidae
Chloropidae
Sepsidae
Muscidae
Piophilidae
Dolichopodidae
Encyridae
Histeridae
Silphidae
Trogidae
Staphylinidae
Cleridae
Dermestidae
Carabidae
1
Time since Death (Days)
2 3
4
5
Lucilia illustris
Phormia regina
Cochliomya macellaria
Chrysomya rufifacies
Protocalliphora sp.
Opsodexia sp.
Phaenicia caprina
A
A
A
A
A
A
A
A/L
Species 1
Species 2
Species 3
A A
A
A
A
6
7
A/L A
L
A
9
11 12 14
15 17 19
22 24
A
L
A
A
A A/L A A
A
A
A A
A
A
A
Species 1
Species 2
Sepsis sp.
Musca domestica
Species 2
Protopiophila latipes
Sciapus sp.
Tachinaephagus
zealandicus
Species
Species 1
Omorgus sp.
Necrobia
Dermestes
A
A
A
A
A A
A
A
A A
A
A
A
A
A
L
A A
A
L
A
A A
A
A
A
L
A
A
A
A = Adult
L = Larva
An Easy Science Project For Students
Objectives:
To examine insect
succession on chickens
that have been placed in a
field at the ASU farm
complex.
Students were responsible
for designing and doing
the experiment.
Materials and Methods
This experiment was conducted
from 18 September – 12 October
2007.
Dead chickens were donated from a
poultry producer in the area.
Four chickens were used in this
experiment (weighed 8-10 lbs).
Chickens were placed in cages to
prevent scavenging by other
animals.
Cages could be opened from the
side and top for easy access.
A rock was placed on each
cage to prevent the cage
from being moved by
predators.
Two cages were placed next
to trees.
Two cages were placed in a
more open environment.
Vegetation around the cages
was identified.
The amount of sun exposure
during the day was also
estimated for each cage.
Insects were collected on a
daily basis for the first two
weeks of the study.
After two weeks, insects
were collected every other
day.
Insect collecting techniques
used:
Aerial nets
Forceps
Hands
Collecting jars
Vials with alcohol
Insects will be identified to
species.
Insects Collected
Blow flies – Adults and larvae
Ants
Sepsis sp.
Rove beetles
Dermestidae
Flesh flies
Forensic
Entomology
Formulate
conclusions
Little research
on forensic
entomology in
AR
Develop a
hypothesis
Analyze the
results
Design the
experiment
Test the
hypothesis