44

N. Chari et al.

trachea and nerve floating in blood space. This clearly indicates that the insect wing

is a living membrane covered by a cuticle on both sides.

Wing Venation [3]

1.

In small insects, the venation is greatly reduced as in chalcid wasps.

2.

In the wings of grasshopper and crickets, branching of the veins produces

accessory veins or intercalary veins between the original veins.

3.

Large numbers of cross veins are found in dragonflies and damselflies forming

a reticulum.

4.

All winged insects are supposed to have evolved from a common ancestor, the

“archedictyon”. The hypothetical scheme of wing venation represents (Fig. 4.3)

the “template” that has been modified by natural selection for more than 200

million years in different orders of insects.

5.

Wing venation helps in the classification of insect orders which is listed below

in Table 4.1.

The basic longitudinal veins which can be distinguished from the leading edge of

the wing are shown in Figs. 4.3 and 4.4. The veins are named after the Comstock–

Needham System.

The wing also has some folds. The wing venation helps in the classification

of insects and contributes to the aeroelastic properties of the wing in flight. The

geometry of the wing is variable in many orders. The fundamental basic plan of

Fig. 4.3 Wing venation

(The Comstock–Needham

System)

Table 4.1 The classification of veins

Costa

(C)

First longitudinal vein, the leading edge of the wing

Subcosta

(Sc)

Second longitudinal vein (behind the Costa), typically un-branched

Radius

(R)

Third longitudinal vein, one to five branches reach the wing margin

Media

(M)

Fourth longitudinal vein, one to four branches reach the wing margin

Cubitus

(Cu)

Fifth longitudinal vein, one to three branches reach the wing margin

Anal veins (A1, A2, A3) Un-branched Veins behind the cubitus