12 INTRODUCTION, 



nervure is another nervure extending from the base of the wing to near the hinder angle, 

 and without branches, called the suhmedian novurc (c). This nervure is occasionally (especi- 

 ally in the rapilioniJic and Morphina) joined to the median nervure near the base, by a 

 short connecting nervule, termed the intei'no-tueJia)i 7iei~cnde (not shown in the plate). Lastly, 

 between the submedian nervure and the inner margin is occasionally found a short nervure 

 from the base, often not extending to the inner margin, and called the internal ncrvm-e (f). 



This net-work of branches greatly facilitates exact description of the distribution of the 

 colours and position of the markings, and of the various sexual appendages which are found on 

 the wings of Butterflies, the latter chiefly in the males. When the names attached to the various 

 margins, nervures, and nervules are impressed on the memory, the terms denoting the various 

 areas will be readily understood. Broadly speaking the wing is divided, for purposes of de- 

 scription, into the following areas:— (l), the costal area, between the costal nervure and costal 

 margin ; (2), the subcostal area between the subcostal and costal nervures ; (3), the discoidal cell ; 

 (4), the interno-nicdian area between the median and submedian nervules ; (5), the internal area 

 between the submedian nervure and the inner margin; (6), the basal area comprising the 

 portion of all the above areas nearest to the base ; (7), the apical area near the apex ; and (8), 

 the marginal area along the outer margin. The remaining portion of the wing between the 

 discoidal cell and the marginal area is often loosely called the disc or discal area ; but for 

 greater accuracy it is usual to define the interspaces between each pair of neivules. Thus, the 

 space between the first and second median nervules is termed \\\e. first tiiedian interspace ; that 

 between the second and third, the second median interspace ; that between the third median 

 and lower discoidal nervules, i\\& third mediant interspace ; that between the lower and upper 

 discoidal nervules, the lower discoidal interspace ; and that between the upper discoidal and last 

 subcostal nervules, the upper discoidal interspace, and so on. 



The following expression used in describing also require some explanation. When the 

 term both wings is used it refers to the fore and hindwings of one side, not both forewings or 

 both hindwings. The length of a wing is measured from the base to the apex ; the breadth 

 from the hinder angle to the costa ; the expanse is usually taken as twice the length of the 

 forewing plus the breadth of the body. A band or stripe of colour is said to be longitudinal 

 when it is in the direction of the length of the wing, and transverse when it is in the direction 

 of the breadth of the wing, whether fore or hind : thus a transverse band on the hindwing 

 can be nearly parallel sometimes to a longitudinal band on the forewing : a macular band is a 

 band evidently composed of coalescing spots, and a himtlar band is one evidently composed 

 of coalescing lunules. 



The classification of Butterflies is not of course based on the features of the perfect insect 

 only. The egg, as has been noted above, aff"ords no indication of the afifinities of the perfect 

 insect, though, judging from analogy, it is possible that further investigation may remove this 

 apparent anomaly; but the other stages of caterpillar and chrysalis furnish important, and 

 perhaps even more critical, tests of actual affinity than the last or final stage does. In a hand- 

 book of this sort the distinctive characters of the perfect insect are more prominently put 

 forward in any case, on account of the perfect insect being more accessible to beginners in the 

 study ; and in this particular instance the characters of the earlier stages of Indian Butterflies, 

 being so little known comparatively, it would be premature to attempt to give them the first 

 place, but it is essential to note that the classification, though based nominally on the perfect 

 insect, must be considered as open to revision, when it is found that it entails anomalous group, 

 ing of the earlier stages. Generally speaking it will be found that this is not the case, and 

 that the genera, as now defined, group together caterpillars and chrysalises of the same general 

 types and habits. 



The sexes of Butterflies differ frequently in colouring, and almost .nlways in outline of wings 

 and size ; the female being usually the larger, and having the wings, especially the forewing, 

 broader and more rounded than in the males. But independently of colouring and outline, and 

 also of internal structure, which can only be investigated by dissection under a microscope, there 

 are in most instances external structural features by which the sexes can, with certainty and 



