H1: Introduction to insects
1. Tree of life
Bacteria + archaea: prokaryotes archaea more related to eukaryotes!
Eucarya: DNA with histone proteins + membrane-bound nucleus + symbiogenesis
(mitochondria)
Opisthokonta lead to evolution of all animals!
Most animals are protostomes (Echinodermata + Chordata: deuterostomes)
Arthropoda: biggest phylum + tardigrades & onychophores are sistergroups
Insects arose from group within crustaceans remipedia + branchiopoda most related to
insects than other crustaceans
MOST GROUPS ORIGINATED BEFORE THE PRECAMBRIUM!
Trilobita= early arthropods living in the Cambrian era (>500 MYA) extinct at end of permian
INSECTS: ALREADY PRESENT IN ORDIVICIAN/SILURIAN!
2. Arthropod characteristics
Exoskeleton Protection against diseases + predators + evaporation
(cuticula) Anchoring site for skeletal muscles
Limiting body volume growth
Molting process Shedding of external cuticular layer
(ecdysis) Cyclical event, hormonal regulation
Complex eyes 1.Multiple ommatidia own lens system + photoreceptors + pigment
cells (nerve fibres bundled in optic nerve to NS)
2. Ocelli: detection light-dark + orientation to light source
Coelome reduction Coelome= body cavity surrounded by mesodermal tissue
Open circulatory Hemolymph pumped around by heart
system
Nervous system Double chain of segmentally arranged ventral ganglia fused
Paired jointed Legs + antennae
appendages 1 pair per segment
IN EVOLUTION: EXOSKELETON IS PRIMARY FACTOR IN ARTHROPODISATION!
3. Cuticular processes during molting
Epidermis/hypodermis= skin layer underneath cuticle produces cuticle towards exterior
Epicuticle= waxy lipid-containing upper layer avoids evaporation + protects against invading MO +
role in communication
Oenocytes= epidermal cells that fluctuate in size during molting
cycle produce waxy product that ends up in epicuticle
1. Apolysis: epidermal cells detach from old cuticle
exuvial space
2. Epidermal cells secrete fluid with degrading proenzymes
1
, 3. Attack inner layers of old cuticle degradation endocuticle (soft)
4. Degradation of exocuticle + pressure from inside old cuticle breaks
5. Production new procuticle
6. Fore + hindgut: take old cuticle + molting fluid back up
7. Sclerotisation: hardening cuticle
Alpha-chitin= N-acetylglucosamine units in different chains (antiparallel position) crosslinking
proteins during sclerotization
4. Insect anatomy
A. Skeleton
1.Tergum: dorsal sclerite
2.Sternum: ventral sclerite
3.Pleuron: weaker regions between cuticle (no sclerotization)
Part of cuticle invaginates inside (apodeme): attachment site of
muscles
Calcium carbonate deposition to make it hard!
B. Bodyplan
1. HEAD: antennae (1 pair) + mouthparts
2. THORAX: legs (3 pairs) + wings (2 pairs) on mesothorax + metathorax
3. ABDOMEN: visceral organs
Legs:
Coxa Trochanter Femur Tibia Tarsus Metatarsus
Mouthparts:
1) Mandibles (paired) crush food
2) Maxillae (paired)
3) Labium (unpaired): 2nd pair of maxillae, fused at midline food uptake + finding and sensing
food
4) Labrum (unpaired) covers all mouth parts
5) Hypopharynx
Tympanal organ Ears that sense vibration
Spiracles Connection with trachea
Tracheal system Gas exchange
Trachea connect to every cell each cell in body has own supply of
O2 ( humans!)
Lined with cuticle
Crop Storage of food
Gastric ceca Produce digestive enzymes into midgut
Brain Fusion of supraoesophageal ganglia
Perceives info from antennae
Dorsal vessel Heart pumps hemolymph around
Palps + antennae Sensory organs
Ventral nerve Connects ventral nerve ganglia
chord NS in ventral region
2
, Fat body Storage of energy-rich nutrients
Extensor muscle Extends tibia of legs
Flexor muscle Bends tibia of legs
ANTAGONISTIC ACTIVITY
Malpighian Secrete ions + uric acid (N metabolism) from hemolymph into lumen
tubules Delivered into faeces in small amount of water
Generate fluid in countercurrent: backwards to gastric ceca + taken up
again
Mixing digestive enzymes + reabsorption nutrients
Rectum: reabsorption water + useful molecules dry faeces!
Flying muscles:
Direct + indirect flight muscles Indirect flight muscles
locusts + dragonflies flies + midges
1. Muscles attached to hinges 1. Muscles attached to thorax
of wings 2. Contraction changes shape of thorax
2. Contraction moves 3. Affects hinge region of wings
wings 4. No direct flight muscles needed!
Sensory organs:
1) Compound eyes + ocelli
2) Tympanum
3) Mechanosensory hairs
4) Chemosensory perception (odor/taste): antennae + tarsi + mouth parts
C. Nervous system
1. Protocerebrum
2. Deuterocerebrum
3. Tritocerebrum
Corpora cardiaca= paired neurohemal organ close to front end of heart store + release
neurohormones into hemolymph
Corpora allata= production + release juvenile hormone regulate developmental and reproductive
processes
Mushroom bodies/ corpora pedunculata= neuropil structures in
protocerebrum that process sensory information from antennal lobe
olfactory learning + memory
VERY LARGE IN SOCIAL INSECTS!
3
1. Tree of life
Bacteria + archaea: prokaryotes archaea more related to eukaryotes!
Eucarya: DNA with histone proteins + membrane-bound nucleus + symbiogenesis
(mitochondria)
Opisthokonta lead to evolution of all animals!
Most animals are protostomes (Echinodermata + Chordata: deuterostomes)
Arthropoda: biggest phylum + tardigrades & onychophores are sistergroups
Insects arose from group within crustaceans remipedia + branchiopoda most related to
insects than other crustaceans
MOST GROUPS ORIGINATED BEFORE THE PRECAMBRIUM!
Trilobita= early arthropods living in the Cambrian era (>500 MYA) extinct at end of permian
INSECTS: ALREADY PRESENT IN ORDIVICIAN/SILURIAN!
2. Arthropod characteristics
Exoskeleton Protection against diseases + predators + evaporation
(cuticula) Anchoring site for skeletal muscles
Limiting body volume growth
Molting process Shedding of external cuticular layer
(ecdysis) Cyclical event, hormonal regulation
Complex eyes 1.Multiple ommatidia own lens system + photoreceptors + pigment
cells (nerve fibres bundled in optic nerve to NS)
2. Ocelli: detection light-dark + orientation to light source
Coelome reduction Coelome= body cavity surrounded by mesodermal tissue
Open circulatory Hemolymph pumped around by heart
system
Nervous system Double chain of segmentally arranged ventral ganglia fused
Paired jointed Legs + antennae
appendages 1 pair per segment
IN EVOLUTION: EXOSKELETON IS PRIMARY FACTOR IN ARTHROPODISATION!
3. Cuticular processes during molting
Epidermis/hypodermis= skin layer underneath cuticle produces cuticle towards exterior
Epicuticle= waxy lipid-containing upper layer avoids evaporation + protects against invading MO +
role in communication
Oenocytes= epidermal cells that fluctuate in size during molting
cycle produce waxy product that ends up in epicuticle
1. Apolysis: epidermal cells detach from old cuticle
exuvial space
2. Epidermal cells secrete fluid with degrading proenzymes
1
, 3. Attack inner layers of old cuticle degradation endocuticle (soft)
4. Degradation of exocuticle + pressure from inside old cuticle breaks
5. Production new procuticle
6. Fore + hindgut: take old cuticle + molting fluid back up
7. Sclerotisation: hardening cuticle
Alpha-chitin= N-acetylglucosamine units in different chains (antiparallel position) crosslinking
proteins during sclerotization
4. Insect anatomy
A. Skeleton
1.Tergum: dorsal sclerite
2.Sternum: ventral sclerite
3.Pleuron: weaker regions between cuticle (no sclerotization)
Part of cuticle invaginates inside (apodeme): attachment site of
muscles
Calcium carbonate deposition to make it hard!
B. Bodyplan
1. HEAD: antennae (1 pair) + mouthparts
2. THORAX: legs (3 pairs) + wings (2 pairs) on mesothorax + metathorax
3. ABDOMEN: visceral organs
Legs:
Coxa Trochanter Femur Tibia Tarsus Metatarsus
Mouthparts:
1) Mandibles (paired) crush food
2) Maxillae (paired)
3) Labium (unpaired): 2nd pair of maxillae, fused at midline food uptake + finding and sensing
food
4) Labrum (unpaired) covers all mouth parts
5) Hypopharynx
Tympanal organ Ears that sense vibration
Spiracles Connection with trachea
Tracheal system Gas exchange
Trachea connect to every cell each cell in body has own supply of
O2 ( humans!)
Lined with cuticle
Crop Storage of food
Gastric ceca Produce digestive enzymes into midgut
Brain Fusion of supraoesophageal ganglia
Perceives info from antennae
Dorsal vessel Heart pumps hemolymph around
Palps + antennae Sensory organs
Ventral nerve Connects ventral nerve ganglia
chord NS in ventral region
2
, Fat body Storage of energy-rich nutrients
Extensor muscle Extends tibia of legs
Flexor muscle Bends tibia of legs
ANTAGONISTIC ACTIVITY
Malpighian Secrete ions + uric acid (N metabolism) from hemolymph into lumen
tubules Delivered into faeces in small amount of water
Generate fluid in countercurrent: backwards to gastric ceca + taken up
again
Mixing digestive enzymes + reabsorption nutrients
Rectum: reabsorption water + useful molecules dry faeces!
Flying muscles:
Direct + indirect flight muscles Indirect flight muscles
locusts + dragonflies flies + midges
1. Muscles attached to hinges 1. Muscles attached to thorax
of wings 2. Contraction changes shape of thorax
2. Contraction moves 3. Affects hinge region of wings
wings 4. No direct flight muscles needed!
Sensory organs:
1) Compound eyes + ocelli
2) Tympanum
3) Mechanosensory hairs
4) Chemosensory perception (odor/taste): antennae + tarsi + mouth parts
C. Nervous system
1. Protocerebrum
2. Deuterocerebrum
3. Tritocerebrum
Corpora cardiaca= paired neurohemal organ close to front end of heart store + release
neurohormones into hemolymph
Corpora allata= production + release juvenile hormone regulate developmental and reproductive
processes
Mushroom bodies/ corpora pedunculata= neuropil structures in
protocerebrum that process sensory information from antennal lobe
olfactory learning + memory
VERY LARGE IN SOCIAL INSECTS!
3
