138 ACQUIRED CHARACTERS SEC. 



show a distinct tendency towards the darkening and blacken- 

 ing of the shades of colour, as in the north and on the Alps, 

 and he also stated that the proximity of the sea the moisture 

 of the air therefore seemed to cause this variation. Another 

 lepidopterologist reports (Ibid. 1879) that a moist clayey soil 

 seems in many species to produce a darker colouring. 



I have noticed in my own studies of Lepidoptera that 

 many species of the small islands of the Indian Archipelago, 

 in comparison with their nearest allies of the Asiatic, and also 

 of the European and American continents, are distinguished by 

 remarkably dusky colours. The species of Papilio, Hermocrates, 

 Nonius, and others, with the Australian Leosthenes, in fact 

 form a well-marked dull-coloured group contrasting with the 

 yellow Podalirius and its allies of the continent. The 

 Antiphates forms of the Archipelago are also distinguished by 

 their dark marking. 



On the other hand, the Papilionidse of tropical Africa have 

 strikingly dull, dark shades of colour in comparison with their 

 allies from regions where there is less heat, or less moist heat. 



If we take a general survey of our field- and meadow- 

 flowers in spring and summer we see that in spring, on the 

 whole, the colours white and yellow predominate, while red and 

 blue only appear later in the year. And, indeed, red precedes 

 blue. This is in accordance with the physiological changes 

 of the pigment, which show themselves more or less visibly 

 in many red or blue flowers during their development, and 

 also in some degree in the change of colour which occurs in 

 foliage leaves in autumn. 



What I wish to point out here is that a quite similar substi- 

 tution of one predominating colour for another occurs also, on 

 the whole, in butterflies with increasing warmth of climate. 

 Taking the Papilionidae again as an example, we find those 

 of Europe, North Asia, and North America generally light 

 yellow, or almost white; while in Africa, and to a great extent 



