IXTRODUCTIOX. ix 



neuration. Most Lcpidoptera wliich do not fold the hind-wings together when at rest have one or 

 more short nervures at tlie base of the latter, between the median nervaire and the costa. But in 

 those species which fold the hind-wings, these nervures generally appear as one or more compressed 

 elastic bristles, extending from the membrane of the wing to beyond the costa, and lie behind a 

 border of erected hairy scales on the under side of the fore-wings near the base, so that they serve 

 to unfold the hind-wings when the wings are extended, and to hold them connected with the 

 fore-wings during flight. This bristle is called the frenulum (Fig. 2, lib), and is always single in 

 the male, whereas the female possesses two or more minute and slender bristles. Sometimes the 

 frenulum is present in the male and absent in the female, in which case the latter is unfitted for 

 flight. This structure is only found in the Moths, with the rarest exceptions (the only exception is 

 perhaps an Australian butterfly, allied to the Hespcridcz, which possesses it), so that it is considered 

 to form one of the most weighty characters by which we separate Lcpidoptera into the two main 

 sections of Moths and Butterflies. 



Areas of the Wings. — The wings of Lcpidoptera ma}- be conveniently divided into three areas, 

 or spaces. The first, the basal area (Fig. i, ii.f), occupies the basal third of the wing ; the second, 

 the central area, extends from this to the end of the discoidal cell (Fig. i, ;;//) ; and the third, or 

 marginal area, extends from the e.xtremity of the discoidal cell to the hind margin (Fig. i, sf). 

 These areas are often separated by transverse lines, the position of which determines their extent ; 

 in which case the basal area generally appears to be the smallest, and the marginal area the 

 largest. The central and marginal areas are generally broader on the costa than at the inner 

 margin. 



The Scales of the Wings. — The colour and pattern of the wings are due to the scales. In some 

 genera, such as Sesia, the scales are wanting over a large portion of the wings, which are then 

 colourless or translucent. These scales appear to the naked eye like a fine dust, and their form 

 only becomes visible under a microscope. They are small discs, composed of two, or perhaps three, 

 layers of exceedingly fine membrane, and are attached to the wing by a short stalk, so that they lie 

 over each other in rows, like the slates on a roof, and cover the roots of the next row with their 

 ends. They generally lie flat in one direction, with their ends turned towards the hind margin ; 

 but they are sometimes erect in certain parts of the wing, or opposed to each other, forming small 

 raised patches. Their forms are very different, both according to the species and according to 

 the particular position of the scales. They may vary, from being comparatively broad to very 

 narrow and linear, so as to pass into the form of hairs. One particular kind of scales, called 

 plumules, is only found in certain parts of the wings of some male butterflies {Lycconida in 

 particular), mixed with the ordinary scales. The scales on the hind margin are often more or less 

 deeply toothed. They are not only placed on the surface of the wing, but are also placed on one 

 or more parts of the border, when they are called fringes, or cilia (Fig. \,fr). In the Micro- 

 Lepidcptcra, the fringes are often composed of fine hairs. 



Tlie Pattern of the Wings. — The colours and patterns of Lcpidoptera are very numerous ; and 

 it is only markings of frequent occurrence which have received special names. Among these are 

 lines (linetF), stripes {strigce), bands (vittcB), and fasciee, which are distinguished by their different 

 breadths, the fasciae being the broadest. When they run towards the hind margin they are called 

 longitudinal or basal lines, &c. ; when they run from the costa to the inner margin they are called 

 transverse lines ; or costal lines when they only run a short distance from the costa. When they 

 run more or less obliquely they are called oblique lines. A curved transverse line running through 

 the middle of the wing is called an arched line or stripe (linca arcuata). When a thick band is not 

 sharply bounded it is termed suffused. Short longitudinal lines are called streaks. The lines and 

 ci 



