KHOPALOCEEA. 17 



time) fully exposed, while the upper side is concealed. In Moths the 

 under side of the wings is nearly always duller and paler than the upper 

 side, and any pattern or colouring presented more or less indicates 

 what is on the upper side ; and these Lepidoptera, instead of holding 

 the wings erect over the back, deflect them at various angles when at 

 rest, and for the most part so dispose them that the longitudinally 

 folded hind-wings and the abdomen are covered or roofed by the fore- 

 wings. The only group of Moths containing numerous exceptions to 

 this rule is the Geomctrcey and it is very noteworthy that these alone 

 have the rhopalocerous habit of resting with wings erect. 



A third distinction of Butterflies is their diurnal flight ; but, as 

 certain groups are crepuscular (many Hes2jeridce, some Morphitce, all 

 the Brassolince, and a number of Satyrincc), and as a great variety of 

 Moths in all the great divisions, including some entire Tamilies 

 (Zycenidce, Uranidce), are diurnal in their habits, this can only be 

 taken as much more characteristic of Butterflies as a whole than of 

 Moths as a whole. 



2. Classification. 



A satisfactory arrangement of the Sub-Order is admittedly most 

 difficult to arrive at, the fundamental structure of its members (as 

 indeed may be said of the entire Order Lepidoptera) presenting but 

 comparatively slight modifications, and those being often inconstant in 

 character. As regards the Imago, the most important features from a 

 classificatory point of view are (1°) the neuration of the wings, (2°) the 

 condition of development of the first pair of legs, and (3°) the presence 

 or absence of a second pair of spurs on the hind pair of legs. In the 

 Pupa, the mode of its suspension afibrds the most trustworthy character, 

 while in the Larva the general form, the nature of the dermal append- 

 ages, and the smooth or spined condition of the head, are points of chief 

 importance. It is remarkable that in proportion to the atrophy of the 

 first pair of legs, which is the character in which the higher Butterflies 

 differ most absolutely from all Moths, the chrysalis is free from silken 

 attachments. Thus the pupge of the Hc&p&ridm, the group of Butter- 

 flies in all respects most intimately related to Moths, and whose fore- 

 legs are invariably fully developed in both sexes, are not only attached 

 by the tail and girt with silk, but also secured by many silken threads, 

 which in many cases form a slight cocoon. Those of the Papilionidw, 

 a family which also has the fore-legs perfect in both sexes, are always 

 attached by the tail and also girt ; and, in the case of the remarkable 

 Alpine genus Parnassius, the chrysalis, like those of the Hespcridce iw^t 

 mentioned, is further enclosed by many additional silken threads. It is 

 when we come to the Lijca3nida3, in which, although the fore-legs of the 

 female are perfect, those of the male begin to exhibit the failure of the 

 tarsal articulation and claws, that we first find instances of chrysalides 

 attached by the tail only, but still in a fixed horizontal or slightly 



B 



