9/15/2015

1

Permeability, rigidity, & flexibility as a properties of the cuticle

flexible region as in wing hinge of Schistocerca (locust)

flexible region as in wing base of Lepidoptera

flexible region lacking exocuticle

(membrane)

ecdysial cleavage line (lacks exocuticle)

wedge of partially sclerotized “mesocuticle”

epicuticleexocuticleendocuticleepidermis

fibrous protein

resilin plus chitin lamellae

pure resilin

• (Im-)permeability: lipid monolayer (H2O) & cuticulin (other substances).

• Rigidity: relative thickness of exocuticle & degree of sclerotization.

resilin pad at base of jumping hind leg of a flea

The most “perfect” rubber known:99% efficient & no deformation.

hind wing-folding (Coleoptera)

tibio-tarsal ligament

The rubbery protein resilin

9/15/2015

2

Resilin in the complex wing-folding of Earwigs (Dermaptera)

Labia minor L., unfolding itsright wing (from Haas et al. 2000)

Wing of Forficula auricularia,showing fluorescing resilin patches

and folding lines (dashes)

Note that not all species use their cerci to unfolding or re-fold the wings (Haas et al. 2012).

Derivatives of the integument

• Outgrowths• immovable (no membranous articulation)

• small – microtrichia; secreted sculpturing• large – spines & horns

• movable (in a “socket”)

• medium-sized – setae (macrotrichia)• large – spurs

• Ingrowths• mostly immovable – apophyses & apodemes;

phragmata

• Glands

• Colors

• Sensory structures

9/15/2015

3

Derivatives of the integument (i):Small immovable outgrowths

MICROTRICHIA

Tiger beetle (Cicindellidae)

blunt outgrowths contributing to

sculpturing of cuticle

secreted layers

pore (exit of dermal gland)

SECRETED SCULPTURING

Odonata:damselfly

Two examples of microtrichia

Diptera: Asilidae (robber fly)

seta

microtrichia

9/15/2015

4

Derivatives of the integument (ii) & (iii):Large immovable outgrowths; movable outgrowths

MOVABLEOUTGROWTHS

IMMOVABLEOUTGROWTHS

epicuticleexocuticleendocuticleepidermis

SPUR(multicellular)

SPINE (OR HORN)(multicellular)

MICROTRICHIUM

macrotrichium= SETA

membranoussocket

flexiblesocket

Tormogen cellTrichogen cell

bipolar neuron

Modifications of spines (immovable) and spurs (movable)

Horns in Scarabaeidae(= ‘super’ spines)

tibial spurs

tibial spur

spine

tibia

tarsus

Spurs & spines in Acrididae (Orthoptera)

9/15/2015

5

epicuticleexocuticleendocuticleepidermis

SPUR(multicellular)

SPINE(multicellular)

MICROTRICHIUM

membranoussocket

flexiblesocket

Tormogen cellTrichogen cell

bipolar neuron

The most versatile movable outgrowths: Setae or “hairs”

SETA (macrotrichium)

moveableoutgrowths

Modifications of setae, (a):

saddleback caterpillar

Thoracic hair (Ascalaphidae)

Wing hairs (Thysanoptera)

Wing fringe(cynipid wasp)

Plastron hairs (Corixidae)-- hydrophobic

cuticle

epithelium

Trichogen cellglandcell

Glandular Setae(urticating hairs) seta

…and proprioceptive pads;and nearly all sense organs…

Pheromone brushes(Lepidoptera)

io moth

9/15/2015

6

Modifications of setae, (b):Surface scales

Silverfish (Zygentoma)

Lepidoptera

Lepidoptera

evolutionaryconvergence

socketTormogen cell

Trichogen cell

neuron

transverse ridge

longitudinal ridge

wingsurface

seta

Scales of Lepidoptera:more examples

Silkworm moth (Saturniidae)

Monarch butterfly (Danaidae)

9/15/2015

7

Monarch butterfly

Morphobutterfly

longitudinalridge

transverseridge (rod)

supports(basal struts)

lower lamina(basal platform)

upperlamina

lamellae

Ultrastructure of Lepidoptera scales(striations break down white light into colors)

Derivatives of the integument (iv): Ingrowths(internal rods and ridges)

apophysis

sulcus or suture line

“pit”

(can be hollow)(usually solid)

apodeme or phragma

cuticleepidermis

ingrowth

pit or sulcus

9/15/2015

8

Integumental ingrowths serve as points for muscle attachments

… but also for structural support of parts of the body.The endophragmal skeleton, or endoskeleton,

resists implosion in (a) the head and (b) the thorax

tonofibrillae

muscles attaches tobasementmembrane

(a) Endoskeleton of head: the Tentorium

Psocodea (‘Psocoptera’)

Orthoptera

Tentorium

posteriorarm

anteriorarm

dorsalarm

9/15/2015

9

Tentorium(b) Endoskeleton of thorax (Tettigoniidae)

pleuralapophysis

spinalapophyses

pleural apophysisspinal apo.

Tergum

PleuronPleuron

pleuralridge

Sternum SternumCoxa(leg base)

spinal pit

Hemimetabola(Exopterygota)

Eumetabola(Hemiptera + Holometabola)

Thoracic endoskeleton:Two different cross-sections from winged insects

9/15/2015

10

wax glands; Apidae (bees)

Derivatives of the integument, (V):

Glands

lac glands; Coccidae(Kerria lacca)

…also exuvial glandsand urticating glands.

(India & Thailand)