AMONG THE HEATHER. 109 



insect spies such a cluster, the colour seems 

 to act as a stimulant to his broad wings, just 

 as the candle-light does to those of his cousin 

 the moth. Off he sails at once, as if by 

 automatic action, towards the distant patch, 

 and there both robs the plant of its honey 

 and at the same time carries to it on his legs 

 and head fertilising pollen from the last of its 

 congeners which he favoured with a call. 

 For of course both bees and butterflies stick 

 on the whole to a single species at a time ; 

 or else the flowers would only get uselessly 

 hybridised instead of being impregnated with 

 pollen from other plants of their own kind. 

 For this purpose it is that most plants lay 

 themselves out to secure the attention of only 

 two or three varieties among their insect 

 allies, while they make their nectaries either 

 too deep or too shallow for the convenience 

 of all other kinds. Nature, though eager 

 for cross-fertilisation, abhors ' miscegenation ' 

 with all the bitterness of an American poli- 

 tician. 



