Modules:

• Integument
• Respiration
• Circulation
• Metamorphosis
• Hormones
• Moulting
• Dormancy
• Circadian Rhythms
• Feeding & Nutrition
• Excretion & Water Balance
• Sensing touch, movement & sound
• Sensing taste & odours
• Olfactory Orientation
• Eyes & Vision
• Neural Integration
• Flight & locomotion
• Memory & Learning
• Reproduction
• Semiochemicals
• Bioluminescence
• Thermoregulation
• Insecticides mode of action

Integument

Objectives

At the end of this topic you will:

• describe the structure and function of the insect integument
• describe the types and functions of variations in cuticle composition and form
• know about types of gland cells
• know about silks and other secretions

Topic outline

• Integument Part 1:Structure of and function of cuticle/exoskeleton; Modifications of cuticle: Sclerotization, Colours, Additives, Surface Modifications
• Integument Part 2: Glands; Silks & Secretions, Labial silks, other silks

Activities

• Listen to the introductory mini-lecture on Insect Cuticle. (It is also presented as part of the course, BIOL2205, Insect Science.)
• Additional mini-lectures expand on the topics of modification of cuticle
• Mini-lecture: Insect Glands
• Mini-lecture: Insect Silks

 

Part 1: Structure and function

Mini-lecture: Cuticle from BIOL2205 with references to Gullen and Cranston's "The insects: Outlines of Entomology" Presented by D. Merritt Prepared by B. Cribb and D. Merritt

download video file (m4v) 20MB alternative format (.mov) 20MB download pdf file 1MB audio only (mp3)

Top

Structure of the Cuticle

The integument is a collective term that incorporates the single layer of cells below the cuticle called the epidermis plus the cuticle (cuticle + epidermis = integument).
The epidermis secretes the cuticle.
The procuticle may be differentiated into an endo- and an exocuticle.
It is overlaid by an epicuticle.
Dermal glands and wax filaments extend upwards through the cuticle.

[Modified from Gullan & Cranston, 3rd edition, Fig. 2.1]

	Freeze-fractured cuticle of a weevil showing different orientations of successive layers of microfibrils. Image: with permission R. Giblin-Davis. From: Insect Physiology & Biochemistry, James L. Nation
Cuticle is made up of chitin microfibrils. Chitin is an unbranched amino-sugar polysaccharide. The chitin molecules form long fibrils that are embedded in and linked by a protein matrix. The commonest arrangement of the microfibrils is parallel to one another in sheets, with each sheet differing slightly in its orientation from the previous. This provides strength and retards fracturing. When fractured, it looks like plywood sheets (right).

Top 

Function of the cuticle/exoskeleton

The cuticle has a number of general functions. It can: provide a tough protective covering provide flexibility where needed reduce water loss through the presence of a waxy layer provide antibiotic properties and a barrier to invasion by microorganisms provide a rigid skeleton for attachment of muscles act as ‘tools’ for cutting, grasping, sticking allow perception of the environment (via the senses) provide insulation through production of scales or hairs provide colour through surface sculpturing

Movie: From NatureTech, Smithsonian Channel

Top

Modifications of the of the cuticle

	Sclerotization Image: Richard Bartz Wikimedia Common		Additives: strength & flexibility Image: Bresson Thomas Wikimedia Commons
	Colours & camouflage Image: Richard Bartz Wikimedia Common		Surface modifications Image: Richard Bartz Wikimedia Common

Insect cuticle is providing a model for artificial materials in an area called biomimetics. Biomimetic materials are artificial products that mimic the attributes of natural products, from plants or animals including types of insect cuticle.

• copying the structure of insects’ “foot pads” that allows them to walk on the ceiling
• making flexible cuticle in the laboratory by first producing artificial versions of cuticle proteins and then cross-linking them to make a rubber-like material
• copying the structure of cuticular surface sculpting that produces the brilliant “interference” colours

Top 

Go on to the next section on Integument & glands