COLOUR IN LEPIDOPTERA. 3 



which the great difference in colour and wing-pattern 

 among the Lepidoptera is to be attributed. 



Since my theory is founded on facts observed by my- 

 self, it is absolutely necessary for anybody wanting to 

 judge of it to examine the exactness of the alleged facts. 

 Now this is no light and easy work, requiring a great 

 deal of time besides. As I already pointed out at the 

 beginning of my last paper, one needs to dispose of a 

 sufiBciently large material of Pieridae for consultation, as 

 even good pictures can only partially be used for that 

 purpose. And moreover the capacity to make a good use 

 of such material cannot be dispensed with. One has to 

 know how to read fluently the „biological map", as the 

 wing-pattern of Lepidoptera has sometimes been called, a 

 knowledge only to be obtained at the price of a great 

 amount of study. It is a well-known fact that white people 

 on first meeting with coloured men, do not know how to 

 distinguish the one from the other, and that it takes them 

 rather a long time before they are fully up to it. Yet 

 coloured men's features are respectively just as distinct as 

 ours. As everybody is aware a shepherd knows every lamb 

 of his flock though to others all sheep are alike. With 

 butterflies it is exactly the same thing: one must learn to 

 see their respective difference. Pretending to judge of their 

 colour-variations before knowing this, is just as absurd 

 as a white man pretending to study the expression of 

 mental emotions in the face of a negro, before being able 

 to distinguish several negroes' respective features. Now 

 firstly one must have before one's eyes all or at least a 

 great many species of such genera — as for instance 

 Hehomoia or Tachyris in which the process of colour- 

 change can easily be observed, and then one has to 

 know how to form series by comparison of the occurring 

 colour-phenomena, so as to understand clearly in what 

 manner that change proceeds. This is rather difficult un- 

 less one is used to closely observing butterflies. Another 

 thing required for this comparison is to recollect them, all 



Notes from ttxe Leyden ]VIu.seum, Vol. X^II. 



