THE FLOWER AND THE BEE 



corner. What a wealth of sweetness going to waste ! Fruit- 

 growers have learned from experience that the wild bees are 

 wholly insufficient to gather the pollen and nectar of extensive 

 plantations of fruit-trees, berry -bushes, and cranberries; and 

 effective pollination is secured only by the establishment of 

 apiaries of the domestic bee. An immense quantity of pollen, 

 which can be used by bees in emergencies, is produced by ane- 

 mophilous plants, as the Amentacece, elms, grasses, sedges, 

 rushes, and a variety of homely weeds. Occasionally honey- 

 bees by thousands do resort to anemophilous flowers for pollen; 

 and much less frequently, because their necessities are less, 

 the solitary bees. Many plants have probably remained wind- 

 pollinated, while others formerly entomophilous have wholly, 

 or in part, reverted to self-fertilization or anemophily in the 

 absence of sufficient pollinators. 



If severe competition did exist among the solitary bees for 

 flower-food, the oligotropic habit would not be desirable. 

 It is not an advantage for a bee to restrict its visits to one 

 kind of flower unless it is always certain to obtain the food 

 supply it requires; otherwise it is clearly at a disadvantage as 

 compared with the polytropic species. If severe competition 

 is introduced by artificial means, as by overstocking a locality, 

 then the oligotropic bees will either tend to disappear or become 

 polytropic. The small number of oligotropic bees reported 

 from central Europe is noteworthy. If, however, a very com- 

 mon flower yields a surplus of food then a bee with a period of 

 flight nearly coinciding with the period of inflorescence would 

 save time and labor by restricting its visits to this species; 

 and since bees instinctively learn from observation it would 

 naturally be expected that the oligotropic habit would be 

 formed. According to the theory proposed by the writer 

 certain bees have become oligotropic because of the direct 

 advantage gained, combined with a short term of flight, or a 



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