Notes de cours
Lecture notes/summary of ENT-21306
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This file contains all information needed to prepare yourself for the exam of the course 'Insects as Food and Feed' (21306). Good luck studying :)
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Lecture 1: Introduction● The exam weighs 65%, the case study for 35%.
○ The exam is a multiple choice exam, consisting of 60 questions. It will take place on
campus, with your own device.
● For both the exam and the case study you will need to score a 5.5 or higher.
● For the practical you will
need a pass.
● By using insects as food
and feed, this will contribute
to circularity.
● Insects are able to convert
bio waste streams into
animal body mass.
● Insects are very diverse.
● Insects are invertebrate animals that have an exoskeleton and six legs.
● They are the only winged invertebrate animals.
● Insects are cold-blooded: poikilotherm/heterotherm.
- Poikilotherm: insects can have many
temperatures; they follow the
temperature of their environment.
- Heterotherm: upon measuring the body
temperature of the insect, you will find
various numbers.
● Insects undergo metamorphosis:
transition between larval and adult
stages.
● Insect respiration makes use of a
tracheal system filled with air.
○ They don’t have a closed blood
vessel system, nor do they
have lungs.
○ They have a finely branched tubular system that runs through the whole system. The
finest branches end in the individual body cells.
● Insects have a less centralized nervous system. They have a ventral nerve cord.
- Dorsal vessel (heart): pumps blood from the posterior part of the body to the head of the
insect.
● Insects fulfill important functions in the ecology of different, larger (terrestrial) ecosystems (not
marine ecosystems). We call these functions ecosystem services.
○ Pollination service of plants → plant reproduction.
■ Honey bee.
○ Waste biodegradation service → manure problem in Australia in 1788 was solved
by the import of dung beetles.
○ Natural/biological control in (agro-)ecosystems → they can control the
populations of other organisms.
■ Parasitoids.
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,● Products that insects make:
○ Silk.
○ Wax.
○ Chitin.
○ Resilin.
○ Cochenille (E120).
○ Honey, Royal Jelly, Propolis.
○ Food and feed.
● Technological and medical applications:
○ Silk, protein structure.
○ Nest climate control.
○ Biosensors for explosives, drugs, contaminants.
○ Medical applications (e.g. chitosan, antimicrobial peptides).
● Only 0.1% of all insects are estimated to be harmful.
● There are around 2100 edible insect species.
○ Mainly beetles, caterpillars and wasps, bees & ants.
- Palm weevils:
● Family of beetles. They feed internally on wood.
● Pests of palm tree cultivation → they are specialist consumers of palm trees.
● Each continent has its own species.
● Only the larvae are eaten
- Mopane caterpillar:
● Consumed in southern regions of Africa.
● They also feed on trees.
● Seasonal occurrence in nature of these trees → no plantations.
● They are sold at local markets in their dried form.
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,- Weaver ants:
● They occur in Laos.
● They occur in trees, in large nests. They weave leaves together, and in these nests they
produce colonies.
● They occur so abundantly, that there will never be a depletion of population. No local
extinction will take place.
● Biological control agents.
- Grasshopper:
● They occur in Mexico.
● They are pests of maize and beans → locusts plagues in Africa.
● Harvested early in the morning.
- Hemiptera:
● It’s a giant water bug, which occurs in Laos.
● They contain many essential fatty acids.
● Traditional consumption of insects mainly takes place in the tropical regions.
○ In the tropics, insect species are larger.
○ In the tropics, insects are present in larger quantities → easier to harvest.
○ In the tropics, people have a stronger connection with nature.
○ Insects have a negative image in western societies.
○ In the tropics, insects are considered tasty and healthy.
● It depends on your culture, what you consume.
● There are 2 focal insect species:
○ Black soldier fly: Hermetia illucens L.
■ Only the larvae are consumed.
■ Currently only used for feed purposes.
● Fixed number of larval stages: 6.
○ Yellow mealworm: Tenebrio molitor L.
● The life cycle of the mealworm takes approximately 3-6 months.
The number of larval stages depends on food quality (9-12).
○ In general, the higher the food quality, the lower then
number of larval stages.
● Both insect species have a pupa stage in between the larval and
adult stage.
- Cuticle: skin of animals/exoskeleton.
● There are 2 major developmental pathways, depending on the order of insects.
1. Exopterygota → the insects do not have complete metamorphosis → no pupal
stage. The wings are visible when they’re nymphs.
● Example: Hemiptera.
● Order: apterygota: wingless, no metamorphosis.
2. Endopterygota → the insects have complete metamorphosis → they have a pupal
stage.
● Order: pterygota: with wings.
● Major orders:
○ Lepidoptera: butterflies, moths.
3
, ○ Diptera: flies.
○ Hymenoptera: wasps and bees.
○ Coleoptera: beetles.
● The boyd of an insect consists of 3 major parts:
○ Head.
■ Contains sensory organs and the brain. Food ingestion.
○ Thorax.
■ Wings and legs for movement.
■ 3 segments.
○ Abdomen.
■ Digestion, reproduction.
■ 8+ segments.
- Exoskeleton/cuticle: protective cage/skin of the insect.
● Primary functions:
○ Muscle attachment.
○ Growth restriction (disadvantage) → very rigid.
○ It serves as a protective barrier against:
○ Water loss.
○ Pathogen influx, natural enemies.
○ Noxious chemicals.
● Secondary functions:
○ Pigmentation.
○ Sensory structures.
○ Reproduction.
○ Excretion.
● The cuticle consists of different layers.
● Composition of the cuticle:
● Basement membrane → epidermis (living cell
layer) → endocuticle → exocuticle →
epicuticle.
○ The epidermal cells contribute to the
excretion of the endo- and exocuticle.
- Endocuticle: this layer is re-used; it’s
absorbed by the epidermal cells, when a
larger, new cuticle is secreted.
- Exocuticle: hard/rigid layer → dependent on
the chemical composition of this layer. It’s the
part of the cuticle that’s left behind → it’s shed
as exuvium (residue of the previous larval
stage).
○ Epicuticle:
■ Waxes on top → essential to
prevent desiccation.
■ Outer layer of the epicuticle: cuticulin.
■ Inner layer of the epicuticle: proteins and lipids.
○ Procuticle (endo- + exocuticle): 50-80% chitin, 50-20% proteins (special proteins,
with a special structure → protection + cross-link function).
● Insect ecdysis (moulding): discontinuous growth.
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