Forensic investigations: Forensic entomology (student dossier)
FSE12 | revised June 2013 | © The University of Western Australia
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Activity 1 – Introducing entomology
You will see a PowerPoint presentation with
pictures of various animals.
Look at Table 1

What it is that the ‘YES’ animals have in
common which is different to the ‘NO’
animals? Discuss this in your group.

One of your group will report on your
findings to the rest of the class.
‘Good vs Bad Bugs’ PowerPoint presentation.
In groups, consider the questions:

Are there good bugs and bad bugs?

What role do insects play in science?

Are insects important in forensic science?
Be prepared to report your thoughts to the
class.
Forensic investigations: Forensic entomology (student dossier)
FSE12 | revised June 2013 | © The University of Western Australia
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Table 1: YES and NO animals
NO
Forensic investigations: Forensic entomology (student dossier)
FSE12 | revised June 2013 | © The University of Western Australia
YES
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Activity 2– Structure and life cycle of flies.

You will see a PowerPoint presentation about the structure and life cycles of flies.

Write down on the placemat the features of insects you can recall from the last lesson.
Activity 3 - Classification Activity
Dichotomous keys are used to identify organisms. A dichotomous key gives two choices.
Depending on the choice made, you proceed to the next couplet indicated at the end of your choice.
For example, if you were classifying the following lacewing insect,
what couplet would you choose, a) or b)?
In this example you would choose a) Many cross veins in wings.
You would then go onto Number 5 where there would be another
couplet with 2 choices.
1.
a) Many cross-veins in wings → 5
b) No obvious cross-veins in wings → 6
The organism is identified by a process of elimination.
Using the dichotomous key below, try and try and identify the Order of the following 5 insects:
INSECT
Wasp
Fly
Forensic investigations: Activity information (teacher information)
FSE10 | revised June 2013 | © The University of Western Australia
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Grasshopper
Beetle
Moth
Forensic investigations: Activity information (teacher information)
FSE10 | revised June 2013 | © The University of Western Australia
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Couplets
Extra information
1
Wings may be hidden
under external elytra
a) 1–2 pairs of obvious wings → 3
b) no obvious wings (many abdominal
segments visible from above) → 2
Order
elytra
2
a) antennae absent
b) antennae present → 3
3
a) long cerci
b) small or no cerci → 4
Diplura
4
a)
Phasmatodea
b)
Antennae may be
difficult to see
stick-like insects, <25 mm length, long
antennae
not stick-like in appearance → 5
Protura
5
a) abdomen constricted to narrow waist
b) abdomen not constricted to narrow
waist → 6
6
a) one pair of obvious wings → 7
b) two pairs of wings → 8
7
a) small antennae
Diptera
b) antennae long and easily seen
Hemiptera
8
a) body covered in dense fur
b) body lacking dense hair → 9
Lepidoptera
9
a) hind legs enlarged for jumping
b) hind legs similar to middle pair → 10
Otheopera
10
a) front pair of wings thickened and hard,
meeting to form elytra
Coleoptera
b) front pair of wings not restricted
Embiidina
Forensic investigations: Activity information (teacher information)
FSE10 | revised June 2013 | © The University of Western Australia
Hymenoptera
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cerci
Activity 4 - Monitoring Temperature
You will monitor the minimum and maximum temperatures for each day.
It is important that you do this carefully as you will use this data later on - Activity 7: Accumulated
Heat.
If the school has a weather station get temperatures from the station OR measure the classroom
temperatures using a maximum/minimum thermometer OR collect information about ACTUAL
temperatures from the newspaper or web.
Record data in Table 2.
Table 2: Minimum and maximum temperatures for 5 consecutive days
Date
Temperature
Maximum °C
Forensic investigations: Activity information (teacher information)
FSE10 | revised June 2013 | © The University of Western Australia
Minimum °C
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Average °C
Activity 5 – Rearing flies: the life
cycle of flies
Methods and Apparatus
Scientists must also carefully think about what
method they will use to test their hypothesis
and what equipment or apparatus they need.
Sometimes there is more than one way to find
out what is happening.
Before you start!
A Forensic Investigator works just like a
scientist.
In the activities in this dossier the method and
apparatus that you need to complete the
activity have been included for you but when
you work on solving the crime in the Crime
Dossier you will need to do this yourself.
Scientists use what is called the Scientific
Method.
One of the reasons that scientists and forensic
investigators use the scientific method is so
their findings can be easily checked and if
necessary tested again. In the case of a
forensic investigator their findings need to
stand up in a court situation so it’s important
that they work in a clear, methodical way.
Hypothesis
The first thing you need to do before you start
this activity is to consider what you think will
happen BEFORE you do the activity or
experiment. You need to try and predict or
guess, based on what you already know, what
the outcome or result of the experiment will
be.
Your prediction or guess is actually called an
hypothesis.
Hypotheses are written as testable statements
about the relationships between or among
variables. Variables are anything that can be
measured.
There are 3 main types of variable.
1. The independent variable is the variable
you purposely change.
2. The dependent variable is the variable
that is being observed, which changes in
response to the independent variable.
3. The variables that are not changed are
called controlled variables.
It is important that the hypothesis is worded
so that it can be tested in your experiment.
Do this by expressing the hypothesis using your
independent variable (the variable you change
during your experiment) and your dependent
variable (the variable that changes in response
and depends on changes in the independent
variable).
For example: ‘My hypothesis is that a constant
temperature of 25 °C [independent variable]
will increase the rate of maggot development
[dependent variable].’
Forensic investigations: Forensic entomology (student dossier)
FSE12 | revised June 2013 | © The University of Western Australia
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Results
It is very important to carefully record your
results. You also need to present your results
in a way that it is easy for other people to see
what you have discovered. Sometimes a graph
gives the best ‘picture’ of your results other
times a table works well.
The example below shows results (data) in a
table and then in graphs. Which is easier for
you to see what the data is telling you?
Table and graphs are from a book: Tufte, E.R. 2001 The visual display of quantitative information.
2nd Edition. Graphics Press, Connecticut, USA
Conclusion
Lastly you will write about what you found
out. This section is called the ‘Conclusion’.
The things that you include in the conclusion
are:

A summary of your results.

State whether you proved or disproved
your hypothesis.

State the relationship between
independent and dependent variable.

Summarize
and
evaluate
your
experimental
procedure,
making
comments
about
its
success
and
effectiveness.

Suggest changes in the procedure (or
design) and/or possibilities for further
experiments.
Forensic investigations: Activity information (teacher information)
FSE10 | revised June 2013 | © The University of Western Australia
the
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Experimental design
Create a hypothesis to be tested, identify the
independent, dependent and control variables,
look at the method designed to determine
these.
Your teacher will give you information about
what apparatus you need for setting up the
dishes.
You will need to measure and record
observations daily.
Design a table to record results in.
Forensic investigations: Activity information (teacher information)
FSE10 | revised June 2013 | © The University of Western Australia
page 10
Activity 6 – using insects to
solve crimes
Your teacher will sort your class into a number
of ‘home groups’.
In your home group you will get a number;
1,2,3 or 4 etc.
You will move from your home group to form
an expert group (all 1’s together, 2’s etc.).
Your group will be given several pieces of
card/paper with the same word on it.
In your expert groups you will all individually
research what the term means.
When you have written down what you think is
a good definition of the term you will get back
together with the members of your expert
group.
Within your expert group you will now pool
your individual research to develop an expert
group definition of the term.
Write your groups expert definition in your
copy of Table 3: Definition Sheet.
Your
teacher will give you this.
You will now return to your home group.
Your home group now has members from at
least 4 different expert groups.
Look at Table 4. It has some definitions typed
into it.
Using the definitions in Table 4 and the
information researched by the experts in your
group, decide which is the correct definition
to match each term.
Report to the class.
Forensic investigations: Forensic entomology (student dossier)
FSE12 | revised June 2013 | © The University of Western Australia
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Licensed for NEALS
Table 4: Three definitions of assorted Forensic Entomology terms.
Carefully read the definitions. Consider the definition that each expert group researched. In the
column ‘Your group’s definition’, write what you consider to be the best definition for each term.
Forensic
entomology term
Definition 1
Definition 2
Definition 3
accumulated heat
Accumulated heat
influences the
development of the
insect
The total amount
of heat required for
an organism to
develop from one
point in its lifecycle
to another point
A certain amount of
heat, accumulated
over time, needed
for some organisms
to grow
degree days
The amount of
accumulated heat
is expressed as
degree days
Average
temperature for
the day
One degree-day is
the amount of
development that
occurs in one day
(24 hours) when the
temperature is one
degree above the
lower development
threshold
faunal Succession
Animals succeed
one another in a
definite,
recognizable order
Insects arrive on a
corpse in a
predictable
sequence
depending on the
stages of
decomposition
The sequence of
insects arriving on a
body
detritivore
The organism gets
its energy form
organic wastes and
dead organisms
An organism whose
food source is dead
or decomposed
organic materials
Consume detritus,
which is dead
organic matter, and
redistribute the
material returning
it to the soil
decomposer
Obtain energy and
nutrients from
organic remains
and waste
Decomposers
secrete enzymes
that break down
organic matter and
then their
individual cells
absorb break down
products
Feeds on and
breaks down dead
plant or animal
matter
post mortem
interval
Time of death of a
person
The time that has
elapsed since a
person has died
The time between
when a person has
died and when
their body has been
found
physiological time
The amount of heat
required for an
organism to
complete its
development
The measurement
of accumulated
heat over time
Measure of how
much heat is
required to
complete a
particular
organisms
development
lower development
threshold
The lowest
temperature at
which development
can proceed.
Temperature that
below development
stops.
The minimum
temperature for
development.
poikilothermic
Poikilothermic
animals cannot
maintain constant
body temperature
Animals that have a
body temperature
that varies with the
environment
Cold-blooded
animals
Forensic investigations: Forensic entomology (student dossier)
FSE12 | revised June 2013 | © The University of Western Australia
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Your group’s definition
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Activity 7 – Accumulated heat
Measure the maximum and minimum air
temperature each day.

This is an extension of Activity 3:
Monitoring Temperature, Table 2.

Transfer the temperature data from
Table 2 to Table 5.

Calculate the Amount of Heat
Accumulated each day.

Use as the lower threshold temperature
10oC.

Subtract the base temperature from the
average daily temperature. These daily
units of heat are called ‘Growing Degree
Days’.
Note:
Particular insects have different temperature
bases, however 10 °C will be designated the
artificial lower threshold temperature.
If daily average temperatures are above 10 °C,
then the degree-days for that day are equal to
the average temperature minus 10 °C.
If the daily max and min temperatures are less
than 10 °C, then the degree days for that day
are 0.
If the average max and min temperatures are
greater than 40 °C (upper temperature
threshold), then the degree-days for that day
are 0.
Forensic investigations: Forensic entomology (student dossier)
FSE12 | revised June 2013 | © The University of Western Australia
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Licensed for NEALS
Table 5: Measuring the amount of accumulated heat, in units of Degree Days, by measuring the
maximal and minimal temperatures of a minimum of 5 consecutive days.
Date
eg
Temperature
maximum °C
minimum °C
average °C
25
12
18.5
Threshold
temperature
°C
10
Growing Degree Day
value
Accumulated Degree
Hours
av temp – threshold
temp
DD x 24 hours
18.5 – 10 = 8.5
8.5 x 24 = 204 ADH
10
10
10
10
10
10
10
Forensic investigations: Forensic entomology (student dossier)
FSE12 | revised June 2013 | © The University of Western Australia
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Activity 8 – Food webs
Your teacher will give you a card and some
string to hang it around your neck. The card
will have an organism named on it.
1. The class will also have a ball of string and
scissors.
2. Try and identify energy (or food) sources.
As each one is identified, pass a ball of
string between the two people. For
example: If you are a cow, and someone
else is the grass. You will take the ball of
string, hold onto one end of the string and
pass the rest of the ball to the grass.
3. The grass will hold onto the yarn and pass
the rest of the ball to ‘what it eats,’ in
this case, the sun. Be sure that the sun is
connected to all the plants.
4. Once the string gets to the sun, cut it off,
and start again in another place.
Continue building the web, making the
relationships as complex as time and numbers
of participants allow.
Activity 9 – faunal succession
There is a board game for you to play in
groups of 4.
Forensic investigations: Forensic entomology (student dossier)
FSE12 | revised June 2013 | © The University of Western Australia
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