1. Insect Morphology

2. Exoskeleton Principal layers Epicuticle Cuticle Epidermis waxy layer
provides waterproofing in/out
delicate, may be scratched
Cuticle
chitinous, sometimes sclerotized layer
Epidermis
cellular layer
the living “skin” with multiple secretory functions

3. Exoskeleton Protection from injury and disease
Control of body fluids (preventing dessication and over-hydration)
Support for muscles

4. Chitin Tough Flexible (not stretchable) Structurally cellulose-like
Covers
Entire body externally
Digestive system (except midgut)
Tracheae (except tracheoles)

5. Exoskeleton modifications
Immovable projections
wrinkles, spines – sound production, predation, etc.
Movable projections
Spurs, hairs/setae, scales – proprioception, external movement
Invaginations
Pits, grooves - indicate location of internal projections

6. Invaginations – Pits, Grooves

7. Directional definitions
Anterior – toward the head
Posterior – toward the tail (caudal)
Dorsal – top or upper side
Ventral – bottom or lower side
Mesal – longitudinal centerline of dorsum or venter
Axial – longitudinal axis of body
Lateral – on side (pleural)
Basal – near point of attachment (proximal)
Apical – farthest from point of attachment (distal)

8. Body Regions Head – prostomium and 4 segments – sensation, ingestion
Thorax – 3 segments – locomotion
Abdomen – up to 12 segments – digestion, circulation, excretion, reproduction

9. Head Positions Hypognathous – mostly chewing herbivores/detritivores
Prognathous – most predators
Opisthognathous – sucking herbivores and predators

10. Head Regions Occiput Vertex Frons Clypeus Genae Ecdysial lines
(frontal sutures +
epicranial suture)

11. Sensing Organs Compound eyes or stemmata - mosaic vision
Ocelli – phenology regulation?
Antennae (scape, pedicel, flagellum) – touch, sound, smell

12. Mouthparts Labrum (“upper lip”) Mandibles (paired) Maxillae (paired)
Lacinia
Galea
Palp
Labium (“lower lip”)
Submentum
Mentum
Glossae
Paraglossae
Palps
Hypopharynx (“tongue”)

13. Thorax
Alinotum = scutum + scutellum
Pleuron
Sternum

14. Leg
Coxa
Trochanter
Femur
Tibia
Tarsus (subsegmented)
Claw(s)

15. Wings

16. Abdomen
Segments I–X visible in most insects
Tergum
Pleuron
Sternum

17. Abdominal Appendages Respiratory structures – gills, siphon
Cerci – tactile processes of abdominal segment XI
Caudal filament – dorsal process of some mayflies
Anal claws – caddisflies, some beetles
Crochets – moths
Genitalia – mating/oviposition structures of adults

18. Metamorphosis Ecologically similar larvae and adults
“Ametabola” = Egg–larva–adult (“incomplete”)
Collembola
“Paurometabola” = Egg–larva–adult (“incomplete”)
Orthoptera, Hemiptera
Ecologically different larvae and adults
“Hemimetabola” = Egg–larva–adult (“incomplete”)
Ephemeroptera, Odonata, Plecoptera
Holometabola = Egg–larva–pupa–adult (“complete”)
Megaloptera, Neuroptera, Trichoptera, Lepidoptera, Mecoptera, Coleoptera, Diptera, Hymenoptera

19. Metamorphosis – Holometabola and “Hemimetabola”