133 



androconial patch on the disc of the upper wing ; the second has 

 two well-defined androconial patches in the upper wing, forming 

 parallel streaks ; and the third has a broad but faint androconial 

 patch on the upper wing, and a large white patch at the basal part 

 of the lower wing. 



Mr. Rothney who took Pademma kollari near Calcutta mistook 

 it for Crastia core, and I have been obliged to submit the female 

 now exhibited to Mr. Moore, to enable me to quiet my doubts as to 

 which species it really belonged. 



These three are all species from continental India ; in Ceylon 

 there are three species of the same genera, exactly bearing the same 

 relationship to each other in colour and markings. They are Crastia 

 asela, Narmada Montana, and Pademma sinhala ; almost the only 

 difference between these three insular and the three Indian species 

 is that the former have less spots than the latter on the upper wing, 

 and the white throughout all the wings is much duller, being, indeed, 

 of a pale brownish white. 



I exhibit the two first-mentioned species, but I have not been 

 able to obtain Pademma sinhala. 



The only explanation of this remarkable isochromatism existing 

 between equally inedible species is that of the late Fritz Miiller. 

 He was of opinion that young anmials had to learn by experience 

 the insects which were palatable and unpalatable, and that, where 

 several unpalatable species closely resembled each other in colour 

 and pattern, that experience might be obtained by tasting one only 

 of the nauseous species, and for the future avoiding that and the 

 others resembling it ; a clear advantage. Shortly, this is how I un- 

 derstand his argument. His view has been accepted by Dr. Russel 

 Wallace and others. 



My experience was not quite in accordance with Fritz MuUer's 

 view, for I always found that when I gave my aviary of birds 

 nauseous larvae, they took not the least notice of them ; many of 

 these larv^ belonged to species that the birds, from their age, could 

 never have seen before, and therefore could have had no experience 

 of their inedibility. 



I was of opinion then, and am still, that birds have an hereditary 

 instinctive knowledge of the relative edibility of insects ; but, in 

 common with many other rules, to this there may be exceptions, 

 and others have made observations showing that birds do sometimes 

 taste nauseous insects. Of course, there might have been a time 

 in the remote history of birds when they were obtaining and per- 

 fecting this hereditary instinct, the isochromatous colouring might 

 have then been a great advantage. 



Mimicry and isochromatism exist far more in tropical and sub- 

 tropical countries than in temperate regions, and as in the former 

 it appears that the struggle for existence is more severe, I feel in- 

 clined to accept, though with some hesitation, Fritz Miiller's theory 

 as, at any rate, a working hypothesis. 



