The encyclopædia britannica; a dictionary of arts, sciences, literature and general information . d by short transverse nervures, so that the wing-areais marked off into a number of cells or areolets. The details of the ncrvuration vary greatly in the different orders,but J. H. Comstock and J. G. Needham have lately (1898-1899)shown that a common arrangement underlies all, six series of longi-tudinal or radiating ner\ures being present in the typical wing (seefig. 5). Along the costa runs a costal nervure. This is followed • ?—~ ? by a sub-costal which some-times shows two main c
The encyclopædia britannica; a dictionary of arts, sciences, literature and general information . d by short transverse nervures, so that the wing-areais marked off into a number of cells or areolets. The details of the ncrvuration vary greatly in the different orders,but J. H. Comstock and J. G. Needham have lately (1898-1899)shown that a common arrangement underlies all, six series of longi-tudinal or radiating ner\ures being present in the typical wing (seefig. 5). Along the costa runs a costal nervure. This is followed • ?—~ ? by a sub-costal which some-times shows two main comes the radial—usuallythe most important nervure ofthe wing—typically with fivebranches, and the median withfour. These sets arise from amain trunk towards the frontregion of the wing-base. Fromanother hinder trunk arise thetwo-branched cubital nervureand three separate analnervures. In the hind-wing ofmany insects the number of radial branches becomes re- ., „ ., „ . „.duced, while the anal area is A/ter QuaJ. Nitm<d well developed and J- M- Dent & Fig. 5.—Wing-Neuration in aCossid Moth. 2, sub-costal; 3,radial; 4, median; 5, cubital;6, 7, 8, anal nervures. undergoes a fan-like foldingwhen the wings are diversity exists in thetexture and functions of foreand hind-wings in different in-sects.; these differences are discussed in the descriptions of thevarious orders. The wings often afford secondary sexual characters,being not infrequently absent or reduced in the female when welldeveloped in the male (see fig. 6). Rarely the male is the winglesssex. In addition to the wings there are smaller dorsal outgrowths of thethorax in many insects. Paired erectile plates (patagia) are borne onthe prothorax in moths, while in moths, sawflies, wasps, bees andother insects there are small plates (tegulae)—see Fig. 3, t—on themesothorax at the base of the fore-wings. Abdomen.—In the abdominal exoskeleton the segmental structureis v
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectencyclo, bookyear1910
