<P> The first indication of the wing buds is of a thickening of the hypodermis, which can be observed in insect species as early the embryo, and in the earliest stages of the life cycle . During the development of morphological features while in the embryo, or embryogenesis, a cluster of cells grow underneath the ectoderm which later in development, after the lateral ectoderm has grown dorsally to form wind imaginal disc . An example of wing bud development in the larvae, can be seen in those of White butterflies (Pieris). In the second instar the histoblast become more prominent, which now form a pocket - like structure . As of the third and fourth instars, the histoblast become more elongated . This greatly extended and evaginated, or protruding, part is what becomes the wing . By the close of the last instar, or fifth, the wing is pushed out of the wing - pocket, although continues to lie under the old larval cuticle while in its prepupal stage . It is not until the butterfly is in its pupal stage that the wing - bud becomes exposed, and shortly after eclosion, the wing begins to expand and form its definitive shape . </P> <P> The development of tracheation of the wings begin before the wing histoblast form, as it is important to note that they develop near a large trachea . During the fourth instar, cells from the epithelium of this trachea become greatly enlarged extend into the cavity of the wing bud, with each cell having developed a closely coiled tracheole . Each trachcole is of unicellular origin, and is at first intracellular in position; while tracheae are of multicellular origin and the lumen of each is intercellular in position . The development of tracheoles, each coiled within a single cell of the epithelium of a trachea, and the subsequent opening of communication between the tracheoles and the lumen of the trachea, and the uncoiling and stretching out of the tracheoles, so that they reach all parts of the wing . </P> <P> In the earlier stages of its development, the wing - bud is not provided with special organs of respiration such as tracheation, as it resembles in this respect the other portions of the hypodermis of which it is still a part . It should be noted, however, that the histoblast is developed near a large trachea, a cross-section of which is shown in, which represents sections of these parts of the first, second, third and fourth instars respectively . At the same time the tracheoles uncoil, and extend in bundles in the forming vein - cavities of the wing - bud . At the molt that marks the beginning of the pupal stadium stage, they become functional . At the same time, the larval tracheoles degenerate; their function having been replaced by the wing tracheae . </P> <P> Most of the nomenclature of insect orders is based on the Ancient Greek word for wing, πτερόν (pteron), as the suffix - ptera . </P>

Diagram of a membranous wing of a cockroach