. A manual for the study of insects. Insects. DIPTERA. 433 it which is crossed by the fine lines is plaited somewhat like a fan and folded over the other portion. By this means the wing, which is fully developed before the adult emerges, is packed within the wing-sheath of the pupa, which is much shorter and narrower than the wing. When the wing is. 4+5 Vila Fig. 506.—Wing of Blepharocera. finally unfolded, it does not become perfectly flat, but slight, alternating elevations and depressions remain, show- ing the positions of the former folds, a permanent record of the unique history of the wi
. A manual for the study of insects. Insects. DIPTERA. 433 it which is crossed by the fine lines is plaited somewhat like a fan and folded over the other portion. By this means the wing, which is fully developed before the adult emerges, is packed within the wing-sheath of the pupa, which is much shorter and narrower than the wing. When the wing is. 4+5 Vila Fig. 506.—Wing of Blepharocera. finally unfolded, it does not become perfectly flat, but slight, alternating elevations and depressions remain, show- ing the positions of the former folds, a permanent record of the unique history of the wings of these insects. Ordinarily the wings of insects, while still in the wing- sheaths of the pupa, are neither longer nor wider than the wing-sheaths, but expand after the adult emerges from the pupa skin. Usually it takes considerable time for the wings to expand and become fit for flight; and during this interval the insect is in an almost helpless condition. In certain caddice-flies that emerge from swiftly-flowing water, the time required for the expansion of the wings has been reduced to the minimum (see pp. 189, 190). In the net- winged midges, which also emerge from swiftly-flowing water, the difficulty is met by the wings reaching their full development before the adult leaves the pupa-skin. It is only necessary when the adult emerges from the water that it should unfold its wings to be ready for flight. The members of this family have three simple eyes. Each compound eye is divided into two parts: an upper half, in which the ocelli are very large; and a lower half, in. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Comstock, John Henry, 1849-1931; Comstock, Anna Botsford, 1854-1930. joint author. Ithaca, N. Y. , Comstock Pub. Co.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectinsects, bookyear1895
