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Chitinous Membranes and Analogous Material

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Fig. 8.2 Basic structure of insect integument (diagrammatic representation from various sources)

The wax layer is present on the abdomen and thorax of pentatomide bugs such

as Tessaratoma javanica (TJ). The wax is also present in some Fulgoroidea,

scale insects and also in honey bees which secrete a large amount of wax which

helps in making a honeycomb.

7.

A trichogen cell is a hair-like sensory projection of the cuticle articulated by

a socket. At the base of the trichogen cell is a nerve ending. Larger hairs and

bristles are the products of specialized epidermal cells [3] (Fig. 8.2).

Based on the sources of chitin, it has two allomorphs in the forms α and β.

These are studied by using infrared and solid-state NMR spectroscopy along with

X-ray diffraction. However, there is a third allomorph, γ-chitin, available in various

resources, but reported to be a variant of α-family, and hence it is least considered.

The α-form is more common in chitinous cuticles, whereas the β and γ forms are

usually found in cocoons [4]. α, β and γ forms of chitin mainly differ in the degree

of hydration, in the size of the unit cell and in the number of chitin chains per unit

cell [5, 6].

The β-chitin anhydrous structures seem to be well established and stable but

remain to be uncertain due to sensitivity towards hydration. Considering this view,

β-chitin may not be suitable for the design of flexible flapping wings.

Properties

Chitin’s physical properties in its pure form include translucent, pliable, resilient and

tougher. The chitin along with calcium carbonate (chitosan) is much stronger and has

a wide range of biomedical and bio-physical applications. A caterpillar integument