"The wings are traversed by a system of _Veins_--tubular structures which serve at once as extensions of the tracheal system, and to form a stiff framework for the support of the wing. In the normal type of _Lepidoptera_ the fore-wings possess three free veins towards the dorsum, termed 1_a_, 1_b_, and 1_c_; a central cell, out of which rise ten veins, numbered 2 to 11, the sides of the cell being known as the upper median, lower median, and transverse veins respectively; and a free subcostal vein, numbered 12; whilst the hind-wings differ from the fore-wings in having only six veins rising from the central cell, numbered 2 to 7, so that the free subcostal vein is numbered 8 (see Plate I., figs. 3 and 4, assumed type of neuration of a Lepidopterous insect). In some forms a forked parting-vein traverses the middle of the cell longitudinally, and a second parting-vein traverses the upper portion, so as to form a secondary cell; but these are more frequently absent or represented only by folds in the membrane. In a few forms there is a tendency to the production of several false veins, termed _pseudoneuria_, appearing as short branches from the subcostal vein of the hind-wings to the costa; these are thickenings of the membrane, and are commonly very irregular and variable, often uneven in thickness or incomplete. Sometimes one of these near the base is better developed and more permanent in character; it is then termed the _præcostal spur_ (see Plate I., figs. 8^9 and 27^9). Modifications in the general arrangement of the veins may arise through any of the following processes, viz.: (1) _obsolescence_, when a vein loses its normal tubular structure, becoming attenuated and reduced in substance, until it appears a mere fold of the membrane (Plate II., fig. 60, vein 5 in hind-wings of _Selidosema_); (2) _stalking_, when the two veins are fused together for a portion of their length from their base, so as to appear to rise on a common stalk (Plate II., fig. 34, veins 6 and 7 in hind-wing of _Hydriomena_); (3) _coincidence_, when two veins are fused together for the whole of their length, so that one appears entirely absent, an extreme form of stalking; (4) _anastomosis_, when two veins rise separate, meet, and are fused together for a certain distance, and then separate again (Plate II., fig. 23, veins 7 and 8 in the hind-wings of the [F] of _Tatosoma_); (5) _concurrence_, when a vein rises separate, runs into another, and does not separate again, an extreme form of anastomosis; (6) _connection_, when two veins are connected by a short transverse bar passing from one to the other, a special form of anastomosis, evolved from the ordinary form under the influence of a tendency to lateral extension (Plate II., fig. 28, veins 7 and 8 in hind-wing of _Paradetis_). Vein 1_b_ in both wings is often furcate at the base.