IN7'R OD UCTION. ix 



The nervures are numbered from behind forwards according to the order in which they 

 reach the hind margin. The inner-marginal nervures are numbered la, ib, and those coming 

 next 2, 3, 4, etc. The cells are also numbered from the inner margin to the first branch of 

 the median nervure, la, ib, ic, and those following 2, 3, 4, etc. Those cells which do not 

 reach the hind margin and are connected with the discoidal cell are called appendicular cells, 

 and are of less importance. By this means it is possible to indicate any part of the surface 

 of the wings laterally. To do this also longitudinally the wings are divided into three areas, 

 called respectively basal, central and marginal. The centre of the wings may be taken as 

 the point where the hinder end of the discoidal cell, or the part towards the hind margin, is 

 situated, and which is often indicated by special markings. 



The arrangement of the colours on the wings shows a great variety of pattern, the chief 

 terms used in describing which are the following: — 



Transverse lines are narrow markings which cross the wings transversely. 



Half lines are similar lines which do not extend across the whole length of tlie wing. 



In the Noctua and other groups the basal and central areas are bounded by simple or 

 multiple transverse lines, which are described as the two transverse lines, or the anterior and 

 posterior transverse lines. 



Usually only the posterior transverse line is continued on the hind wings and may then 

 be called, as on the under side, the curved line. 



In many species there is a half line in the basal area, and a dark stripe in the central 

 area between the two transverse lines and parallel with them, called the central shade. In the 

 marginal area there is often a pale line more or less parallel with the hind margin and bordered 

 on one or both sides with darker: this is called the submarginal line. 



If the transverse markings on the wings are broader they are called bands. The 

 suffused hand is the space between the submarginal line and the posterior transverse line. The 

 spots are either irregular in shape or have a peculiar shape. Thus sagittate spots or arrow- 

 headed spots are small, pointed and triangular, and if larger are called pyramidal spots. 



A Innule is a crescent-shaped spot. 



The claviform stigma is an elongated, hollow spot, rounded at one end. 



The orbicular stigma is a narrow ring differentiated from the ground colour. The eye-spot 

 is a similar ring with a central dot of a different colour to the ring, called the pupil. Eye- 

 spots with a double pupil have two dots in the middle. 



The reniform stigma is like the orbicular but is usually kidney-shaped. Elongated black 

 sagittate spots often occur near the base on the submarginal line between the nervures. The 

 orbicular stigma is usually situated in the discoidal cell, and beyond it is the reniform stigma. 

 They are then called the two stigmata. When the scales are wanting or thin over the whole 

 of the wings, the wings are said to be clear or transparent. 



Lastly we must mention the frenulum, which is found in most night-flying moths. It 

 consists of a spine from the costal nervure of the hind wings, which is divided into several 

 branches. This spine is connected with a hook on the subcostal nervure of the fore wings, on 

 which it is free to move up and down. Consequently if the fore wing is drawn forward it 

 drags the hind wing after it. 



The legs, of which there are three pairs, are attached to the three thoracic segments, 

 and consist of five parts. A more or less globular piece fits into the socket, this is the coxa, 

 and with it articulates a small ring-shaped portion, the trochanter. To this is attached the 

 femur, which is succeeded at an angle by the tibia. To the tibia is joined the foot or tarsus, 

 which consists of five small joints, the first of which is usually the largest, but all are very 

 variable in shape and size. 



The last segment bears the claws, which are often bifid. The end of the tibiae is 

 sometimes provided with one or two pointed appendages or tibial spines. Spurs are horny 

 spines at the end of the middle and hind tibiae, frequently also present in the middle of the 



