XII 



of covering, has faded to a pale yellow by the time that it becomes more or 

 less visible again. On this account the relative paleness of the colours upon 

 a surface upon which dark pigment also appears, is sometimes an indication 

 as to whether the latter is in the evolutionary condition of increasing or of 

 decreasing. It is not however a certain one, as the darkening is sometimes 

 confined to only a portion of the surface. 



Another help in estimating the evolutionary stage of the wings, lies in the 

 colour relics, if these are present. Just as the study of the so-called tails of 

 Lepidoptera leads to the conclusion that these appendages which appear in a 

 great variety of forms, are nothing but the remains of the former more extensive 

 form of the wings to which they are attached, and which have been affected by 

 an evolutionary diminishing process, in the same way colour relics are sometimes 

 found as survivals, still present upon the surfaces, of tints that were formerly 

 present, but which have subsequently partially or completely been destroyed 

 by the process of colour-evolution. Such colour relics have been repeatedly 

 discussed in the introduction to my third monograph. For example the intense 

 darkening of the upper surface of Cyllo Leda L. (see Plate XV fig. 30^ and 30/.) 

 allows spots of red, sometimes already faded to yellow, to be seen on the wings 

 of some individuals, as survivals of the former colour of the whole ; similarly, 

 on the primaries especially, of many forms of Iphias (Hebomoia) parts of the 

 originally general colour remain, as larger or smaller patches of colour which in 

 some females, further advanced in colour-evolution, have already been replaced 

 by a uniform white colour. A particularly interesting relic stripe is that which 

 I have drawn attention to on p. 35 of my monograph on the Pieridae as 

 sometimes left upon the upperside of the primaries of Iphias Glaucippe L. 

 and clearly showing how the succession of colouring has taken place. It can 

 plainly be seen here how an old colour, pushed aside by a new one, is 

 gradually reduced to a narrow stripe, which is finally completely replaced by 

 the new colour. Similar colour relics are also found among the Lycaenidae 

 sometimes as surviving spots of colour, sometimes as narrow stripes, insignificant 

 to the unitiated, the meaning of which becomes clear, however, when interpreted 

 by the above mentioned results of the study of the Pieridae. These relics often 

 make the course of the colour-evolution clear; when we know what the former 

 colour stage has been, we can conclude in which direction the process of 

 change is moving. 



In one remarkable group of the Lycaenidae, peculiar to the Indo Australian 

 fauna, the Gerydinae, a relic-stripe of this kind is found, which throv\s much 

 light upon its evolutionary history. The butterflies of this group are sharply 

 distinguished from the rest of the Lycaenidae by their abnormal legs; a few 



