( liv ) 



butterflies, and Diptera. The question is, How have the odours 

 of this latter class been evolved '? 



" To take a simple instance : I have this summer repeatedly 

 observed two large, flourishing Petunias, covered with bloom. In 

 addition to the rich purple colour of the flowers their scent is 

 very pleasant, resembling that of the Pink and Carnation. But 

 though I often watched the plants in full sunshine, I never once 

 saw any insect enter the flower as if in quest of honey or pollen. 

 Sometimes a cabbage-white or a bee would sail over the plants, a 

 Stjrphus would hover over them, or a blow-fly ( ! ) would settle on 

 the outer margin of the corolla. But no further notice did the 

 flowers receive. By way of contrast, a patch of French poppies, 

 growing between the two Petunias, was abundantly visited, as well 

 by butterflies as by bees. 



" Thus the neglect of the Petunia-flowers was not due to the 

 absence or the scarcity of flower-haunting insects. 



" If, therefore, the colour and the perfume of the Petunia have 

 been evolved in the way of natural selection, the most conspicuous 

 and most odoriferous flowers being preferentially fecundated by 

 some insect, the question arises, what insect ? The most 

 plausible reply is that it must bave been eff"ected by some insect 

 which has not been introduced into Britain along with tlie plant. 

 Further, such insect, as far as perfumes are concerned, must 

 have preferences more nearly approaching those of man than 

 are those of our bees and butterflies. 



"The case of the Petunia is by no means singular. About 

 two vears ago I observed a number of Privet-shrubs in full bloom. 

 The air was saturated with their sugary but sickly odour. The 

 flowers were crowded with hive-bees, humble-bees, cabbage-whites, 

 and small tortoise-shells, and were from time to time visited by 

 other butterflies. By way of contrast, I noticed that among the 

 Privet-bushes there stood a Syriuga, likewise in full blossom, but its 

 flowers, so much more pleasant to the human sense of smell, had 

 scarcely ever an insect visitor. If by chance a bee or butterfly 

 strayed over it seemed plainly a mistake, and the visitor lost no 

 time in getting back to the Privet-flowers. 



'• Now, to the best of my knowledge, neither the Privet nor the 

 Syringa is indigenous to Britain. Hence it is curious that so 

 many of our native insects should have accommodated thmeselves 

 to the Privet but not to the Syringa. 



