Wing is flattened double layered expansion of body wall with a dorsal and ventral lamina
having the same structure as the integument. Both dorsal and ventral laminae grow, meet and
fuse except along certain lines. Thus a series of tracheae, nerves and blood. Wing is nourished
by blood circulating through veins. Later the walls of these channels become thickened to form
veins or nervures. The arrangement of veins on the iwngs is called venation
which is extensively
used in insect classification. The principal longitudinal veins arranged in order form the anterior
margin are costa (C) , sub costa ( Sc), radius ®, median (M), cubitus (Cu) and anal veins (A).
Small veins often found inter connecting the longitudinal veins are called cross veins. Due to the
presence of longitudinal veins and cross veins, the wing surface gets divided into a number of
enclosed spaces rermed cells. In insects like dragon fly and damselfly, there is an opaque spot
near the coastal margin of the wing called pterostigma.
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