76 Colouration in Animals and Plants. 



In the majority of insects the costal margin is marked with 

 strong colour. This may be noticed in Papilio Machaon, P. merope, 

 Vanessa antiopa, and the whites in Plate IV. The extreme tip of the 

 fore-wings is nearly always marked with colour, though this may 

 run into the border pattern. This colour is dark or vividly bright, 

 and we know no butterfly, not even dark ones, that has a light tip to 

 the wings. Sometimes, it is true, the light bead-border spots run to 

 the tip, but these are not cases in point. The development of tips 

 has been traced in Chapter VI, and need not be repeated. 



The hind margin of both wings is very commonly emphasized by 

 a border, of which V. Antiopa, PI. III. Fig. 3, is a very perfect 

 example. 



The border pattern may consist of one or more rows of spots, 

 lines, bands, or scallops ;* and there is frequently a fine fringe, 

 which in many cases is white, with black marks, and to which the 

 term bead-pattern may be applied. 



A definite relation subsists in most cases between the shape of 

 the hind margin and the character of the border-pattern. The plain 

 or simple bordered wings have plain border patterns, and the 

 scalloped wings have scalloped borders ; or rather scalloped borders 

 are almost exclusively confined to scalloped wings. In our English 

 butterflies, for instance, out of the 62 species : — 



33 have plain margins to the wings. In all the border is plain, 

 or wanting. 



20 have the fore-wings plain, and the hind wings scalloped, 

 and in all the hind-wings are scalloped and the fore- 

 wings plain, or with slightly scalloped border-patterns. 

 9 have scalloped margins and scalloped border-patterns. 



Another relation between structure and pattern is found in those 

 insects which have tailed hind-wings, for the tail is very frequently 

 emphasized by a spot, often of a different colour from the rest of the 

 wing as in the S wallow-Tails, Plates IV. and V. 



Yet another point may be noticed. In each wing there is a space, 

 the discoidal cell, j Fig. 3, at the apex of which several nervures 

 join, forming knots. These are points at which obstacles exist to the 

 flow of the contents,and they are almost always marked by a distinct 

 pattern. We thus have a discoidal spot in very many butterflies, in 



* In the true scallop pattern the convexity is turned towards the body of the 

 insect. 



