140 THE ORIGIN OF SPECIES 



up too much space to show the various steps, through 

 -^ dimorphism and other means,i by which the separation of 

 the sexes in phints of various kinds is apparently now 

 in progress; but I may add that some of the species of 

 holly io North America are, according to Asa Gray, in 

 an exactly intermediate condition, or, as he expresses 

 it, are more or less dioeciously polygamous. 



Let us now turn to the nectar-feeding insects; we may 

 suppose the plant, of which we have been slowly increas- 

 ing the nectar by continued selection, to be a common 

 plant; and that certain insects depended in main part on 

 its nectar for food. I could give many facts showing how 

 anxious bees are to save time: for instance, their habit 

 of cutting holes and sucking the nectar at the bases of 

 certain flowers, which with a very little more trouble 

 they can enter by the mouth. Bearing such facts in 

 mind, it may be believed that under certain circum- 

 stances individual differences in the curvature or length 

 of the proboscis, etc., too slight to be appreciated by us, 

 might profit a bee or other insect, so that certain indi- 

 viduals would be able to obtain their food more quickly 

 than others; and thus the communities to which they be- 

 longed would flourish and throw o2 many swarms in- 

 heriting the same peculiarities. The tubes of the corolla 

 of the common red and incarnate clovers (Trifolium pra- 

 tense and incarnatum) do not on a hasty glance appear 

 to differ in length; yet the hive-bee can easily suck the 

 nectar out of the incarnate clover, but not out of the 

 common red clover, which is visited by humble-bees 

 alone; so that whole fields of the red clover offer in 

 vain an abundant supply of precious nectar to the hive- 

 bee. That this nectar is much liked by the hive-bee is 



