Exploring the World of Insects and Arthropods

Exploring the World of Insects and Arthropods
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Slide 1: Slide
Human Regulation and ReproductionFurther Education (Key Stage 5)

This lesson contains 35 slides, with interactive quizzes, text slides and 1 video.

time-iconLesson duration is: 120 min

Items in this lesson

Exploring the World of Insects and Arthropods

Slide 1 - Slide

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Learning Objective
At the end of the lesson, you will be able to:
  • Identify different stages of the life cycle of insects and arthropods.
  • Explain the impact of temperature on insect development.
  • Compare the decomposition stages to insect development.

Slide 2 - Slide

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What do you already know about Forensic entomologists?

Slide 3 - Mind map

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Recap!
A decomposing body follows a regular pattern and predicable changing habitats. The stages include: 
- Fresh
- Bloat/Putrefaction
- Active/Advanced Decay
- Dry/Skeletisation

Slide 4 - Slide

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Forensic Entomologists
Apply their knowledge of entomology to provide information for criminal investigations. Their job may include: 
  • Identification of insects at various stages of their lifecycle.
  • Collection and preservation of insects as evidence.
  • Determining PMI estimate.
  • Testifying in court to explain insect-related evidence.

Slide 5 - Slide

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What does PMI stand for? And what does it mean?

Slide 6 - Open question

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Forensic Entomologists
Insects help forensic scientists estimate how long the victim has been dead. Other uses include:  
  • Movement of the body
  • Manner and cause of death
  • Association of suspects with the death scene
  • Detection of toxins, drugs or even DNA

Slide 7 - Slide

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Introduction to Insects and Arthropods
Insects and arthropods are diverse species that play crucial roles in ecosystems. They encompass a wide range of species, including beetles, butterflies, ants, and spiders.
Did you know? Maggots can be used to test for the presence of poisons or drugs. Some drugs can even speed up or slow down an insects development. 

Slide 8 - Slide

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Slide 9 - Drag question

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Life Cycle Stages
The life cycle of insects and arthropods includes egg, larvae (maggot), 1st instar, 2nd instar, 3rd instar, prepupal stage, pupa (puerperium), and adult (imago). Each stage has distinct characteristics and behaviours. 

A standard life cycle means that it can be 
used as evidence in court. 

Slide 10 - Slide

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How long does it typically take for a blow fly to complete its life cycle?
A
2-4 weeks
B
1-2 weeks
C
3-6 months
D
1 year

Slide 11 - Quiz

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What do blow fly larvae feed on?
A
Decaying organic matter
B
Seeds
C
Nectar
D
Fresh fruits

Slide 12 - Quiz

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What is the first stage of blow fly life cycle?
A
Pupa
B
Adult
C
Larva
D
Egg

Slide 13 - Quiz

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Life Cycle Stages
The main insects used in investigations are in two orders: 
  1. Flies (Diptera) - Specifically blowflies  
  2. Beetles (Coleoptera) - Specifically dermestid beetles
Species succession may also provide clues for investigation. Some may feed on a fresh body, whereas others may prefer to feed on one that has been dead for a length of time.  

Slide 14 - Slide

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Insects of Death
Flies can arrive within minutes. They lay eggs that hatch to maggots. Maggots feed on soft, mushy body parts. More insects arrive to feed on the body and each other. 
             Blowfly                                         Flesh fly                                      House fly

Slide 15 - Slide

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Insects of Death
Some beetles feed on the body, some on maggots, and some on other beetles. 

Slide 16 - Slide

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Blow Fly Metamorphosis

Slide 17 - Slide

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Blow Fly Metamorphosis: Eggs
1st - Adult flies lay eggs on the carcass, especially at wound areas or around the openings in the body such as the nose, eyes, ears, anus, etc. within 48 hours of death.  
2nd - Eggs hatch into maggots (larvae) in 12-24 hours

Slide 18 - Slide

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Blow Fly Metamorphosis: Larvae
3rd - Larvae continue to grow and molt as they pass through their various instar stages. 

  • 1st Instar - Approx. ?mm after ? hours

  • 2nd Instar - Approx. ?mm long after ? days

  • 3rd Instar - Approx. ?mm long after ? days

Slide 19 - Slide

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Blow Fly Metamorphosis: Larvae
3rd - Larvae continue to grow and molt as they pass through their various instar stages. 

  • 1st Instar - Approx. 2mm after 24 hours

  • 2nd Instar - Approx. 11mm long after 2.5 days

  • 3rd Instar - Approx. 15mm long after 5 days

Slide 20 - Slide

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Blow Fly Metamorphosis: Pupa
4th - The larvae develop into pupa after burrowing in surrounding soil or a safe dark space. 
5th - Adult flies emerge from pupa cases after 6-8 days

Slide 21 - Slide

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4

Slide 22 - Video

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Relating flies to the stage of decomposition








Now put this into a cycle or spider diagram to embed your learning. 
Take a photo to upload to the next slide.  
Stage of Decay
Timeframe
What happens in the body? 
What happens with the bugs?
Fresh
0-4 days
Temperature falls, autolysis occurs
Flies begin to arrive
Bloat
4-10 days
Body swells due to gasses, temperature increases
Flies and maggots present
Active/Advanced
5-11 days
Body flattens, bacteria/maggots break through the skin
Larvae begin to pupate
Dry/Skeletonisation
10-25 days
Reduced to hair and bones
Flies reduced and replaced by other arthropods
timer
15:00

Slide 23 - Slide

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Upload your images of your cycles/spider diagrams

Slide 24 - Open question

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00:22
What is the body temperature change also known as?

Slide 25 - Open question

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00:58
What is generally the first type of insect to hone in on a human body?

Slide 26 - Open question

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01:42
What are the different larval stages called?

Slide 27 - Open question

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03:41
What does mass spectrometry allow scientists to produce?

Slide 28 - Open question

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Behavior and Location
The stages of the life cycle significantly impact the behavior and location of insects and arthropods. For example, larvae may have specific feeding habits and habitats, while adults engage in reproduction and foraging.

Slide 29 - Slide

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Effects on Insect Activity
The most important environmental factors in decay:
  • Temperature
  • Access by insects
  • Depth of burial

Flies do not live in the extreme cold

As a rule, the higher the temperature, the faster the decomposition rate.

Slide 30 - Slide

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Temperature Effects
Temperature has a significant impact on the developmental stages in the life cycle of insects and arthropods. It can influence the rate of growth, behavior, and survival of individuals.

Slide 31 - Slide

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Processing a Crime Scene for Insect Evidence
  1. Death-Scene observations
  2. Collection of meteorological (Weather) data
  3. Two collections: Collect live insects, and collect and preserve other insects from the body at the crime scene
  4. After body removal: Collect insects from the surrounding soil.  

Slide 32 - Slide

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Write down 3 things you learned in this lesson.

Slide 33 - Open question

Have students enter three things they learned in this lesson. With this they can indicate their own learning efficiency of this lesson.
Write down 2 things you want to know more about.

Slide 34 - Open question

Here, students enter two things they would like to know more about. This not only increases involvement, but also gives them more ownership.
Ask 1 question about something you haven't quite understood yet.

Slide 35 - Open question

The students indicate here (in question form) with which part of the material they still have difficulty. For the teacher, this not only provides insight into the extent to which the students understand/master the material, but also a good starting point for the next lesson.