3i6 ENTOMOLOGICAL NEWS. [July, '14 



It would be easy to multiply examples in the case of buck- 

 wheat, basswood, tupelo, raspberry, heartsease and golden rod, 

 and the extra-floral nectaries of cotton and Cassia chamae- 

 christa in the Southern States. Certain plants, as Bidens aris- 

 tosa in the lowlands of the Mississippi, fairly carpet large 

 areas with their myriads of flowers. Fruit growers have 

 learned from experience that the wild bees are wholly insuf- 

 ficient to gather the pollen and nectar of extensive plantations 

 of fruit trees, berry bushes and cranberries; and effective pol- 

 lination is secured onl}^ 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 anemophilous 

 plants, as the Amentaceae, elms, grasses, sedges, rushes, and a 

 variety of coarse 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. 



In none of his articles has Robertson ever presented satis- 

 factory evidence of existing competition for flower food; and 

 in reply to my earlier paper he now advances the hypothesis 

 that oligotropism originated at some indefinite past time in the 

 evolution of the long-tongued pygidial bees and Andrenidae, 

 etc., from the competition of the former with the Bombidae 

 and of the latter with the Halictidae. This highly imaginary 

 supposition can not be supported by historical data, and would 

 appear to be neither probable nor necessary. The polytropism 

 of Halictus is the result of its peculiar economy. The im- 

 pregnated females hibernate during the winter and appear the 

 following spring ; while the new generation flies during the 

 latter half of the season. This economy has no special ad- 

 vantage for Halictus is greatly surpassed by Andrena in both 

 species and individuals ; while Sphecodes which has essen- 

 tially the same economy as Halictus is represented by com- 

 paratively few species and individuals. It is an advantage for 



