IxTRODUCTio.v. vii 



projecting fold. There are several variations to be noticed in the hind margin. As regards its 

 general shape, it is called straight on the fore-wings when it runs in a nearly straight line 

 from the tip to the hinder angle (Fig. ii,Sin); arched when it is curved outwards (compare the 

 right fore-wing in Fig. i) ; or sinuated when it is curved inwards at any point (see the fore- 

 wing in Fig. 2); angulated when its outline forms distinct angles; and indented when it 

 has large and deep indentations. It is also called entire when it forms a simple, curved, or 

 sinuated line (Figs. 31 and 32); undulated when it curves slightly outwards at the end of 

 each nervure, and thus forms a sort of wavy outline (see the right fore-wing in Fig. i) ; 

 dentated when it consists of small roundish indentations, meeting in sharp angles at the ends 

 of the nervures (compare the left fore-wing in Fig. i) ; and lobed when it consists of rounded 

 projections which meet towards the base in acute angles between the nervures (as in the left 

 hind-wing in I"ig. i). 



Ncuration of the zvings. — The arrangement of the nervures of the wings is very important, 

 .not only for the purposes of classification, but to enable us to point out any particular part 

 of the wing with as much exactness as possible. The nervures either rise from the base 

 of the wing, or from other nervures ; and, in the latter case, generally in consequence of one 

 nervure dividing into several. All nervures which do not rise from the base are called 

 branches, or nervules. The first nervure running from the base forms the costa itself, and 

 does not require any special name. Two nervures rise close together from the middle of 

 the base, and diverge from each other, throwing off several branches. They are generally 

 united at or beyond the middle of the wing by two, or, in the PapilioiiidcB, three, short 

 transverse nervules called the disco-cellular nervules (Fig. i, qa). The first of these diverging 

 nervures is called the sub-costal nervure (Fig. \,vnir), and that nearest the inner margin 

 the median nervure (Fig. ijiiiir). These names apply as far as the disco-cellular nervules. 

 Another nervure rises from the base, between the costa and the sub-costal nervure, which 

 finally unites with the costa, and is called the costal nervure (Fig. i, R\2 and A'S). In 

 the hind-wings it often touches the sub-costal nervure near its origin, or is united with 

 this for a short distance, or it may be absent altogether (as in Fig. 32). In manj' species, 

 especially those in which the hind-wings are not folded when at rest, there are one or more 

 nervures, which are generally short and curved, at the base of the hind-wings, close to the 

 costa. There are also from one to three nervures running between the riiedian nervure and 

 the inner margin, which run from the base either to the anal angle, or the inner margin, or 

 the hinder part of the hind margin. These are called the sub-median nervures, and there is 

 generally only one on the fore-wings (Fig. i, R\), which is often forked near the base, and more 

 rarely near the hind margin (Fig. 33, R\). Sometimes there is a second between this and the 

 median nervure (Fig. 31, la and \b), which is generally conspicuous only near the hind margin, 

 and passes into a mere seam towards the base. In the hind-wings there are generally two 

 sub-median nervures (Fig. i, \a and \h). In many genera, especially among the 3Tkro- 

 Lepidoptcra, there are three (Fig. 31, \a, \b, and ir), the second of which often forms a short 

 fork near the base ; and there is seldom only one on the hind-wings. We often find one or two 

 more fine nervures between the sub-costal and median nervures, which run from the base to the 

 disco-cellular nervules, and are frequently only visible at their extremities (Figs. 31, //•, and t,Ti, tr). 

 The difi"erent nervules branch either from the sub-costal or median nervure, or from the 

 disco-ceOuIar nervules. In the former case they often do not rise from the nervure itself, but 

 from one of its branches. The sub-costal nervure of the fore-wings generally throws off six 

 branches in this manner, and that of the hind-wings two, which run to the costa and hind margin. 



