scaffold for strength, muscle attachments

• pleural (suture) (example)• critical for flight

Two major sections:

1. epicuticle2. procuticle

epidermal cells

• Epicuticle –made up of cuticulin and inner epicuticle

epicuticle

epidermis and associated cells

• epidermal cells• glandular cells• oenocytes

Basic unit of chitin is n-acetylglucosamine

β - linkage

Chitin makes up as much as half of the exoskeleton

forms long chains

chains interact with each otherhydrogen bondsform microfibrils

Across insect cuticle, sclerotization varies

• Exocuticle = hardened region

• Endocuticle= not hardened

Exocuticle

Endocuticle

Degree of sclerotization varies in different body parts, stages,

species … etc

Regions of unsclerotized cuticle give points/lines that can bend

a cuticle protein

• “cleft” full of aromatic residues, which form “flat”surfaces of aromatic rings, for protein–chitin interactions

• outer surface (lower side) important for protein–protein interactions in cuticle.

A protein in hard cuticle

• Histidines (blue) are in right position to participate in sclerotization

• Or to be involved in water binding capacity of cuticle

A protein in soft cuticle

• lacks histidinesfor sclerotization

Young’s modulus

= stiffness

Dermaptera• very important in

wing flexibility and resilience

• blue areas contain resilin

engineers at work

Pore Canals

epidermal cells have extensions that reach up through the epicuticle

Multilayer reflectors

Seago A E et al. J. R. Soc. Interface 2009;6:S165-S184

©2009 by The Royal Society

• layer spacing has peak green reflectance

• the broader the range of thicknesses, the closer to pure silver or gold

The iridescent scales of the Morpho sulkowskyi butterfly give a different optical response to different individual vapours. This optical response dramatically outperforms that of existing nano-engineered photonic sensors.

What happens if these cells make new cuticle?

• It will be the same size as the one before

• FIRST, cell division!

APOLYSIS-separation of old cuticle

from epidermis, formation of space

• Molting fluid

• New cuticulinand epicuticle

Enzymes activatedInner epicuticle produced

Endocuticledigested

Fluid reabsorbed

Procuticle laid down

ecdysis

Expansion, sclerotization