418 C. H. TURNER 



1. There is no evidence to support Robertson's contention 

 that Epiolus is a parasitic genus. 



2. To Robertson's assertion that a strenuous struggle for food 

 is the determining factor in the evolution of the habits of bees, 

 he replies that the size of the bee fauna is limited by other 

 factors than the food supply. He insists that the commonness 

 of an insect species does not depend alone on the quantity of 

 available food, and gives the following specific proofs that only 

 part of the available food is gathered by bees: — (a) In River- 

 side County, California, the orange bloom secretes nectar so 

 freely that it drops upon the teams and clothing of the pruners 

 in such copious amounts that, at the close of the day, it is neces- 

 sary to wash the horses and the harness, (b) Hundreds of acres 

 of the sandy coastal plain of Georgia are covered with bushes 

 of the common gallberry (Ibex glabra). It is in bloom for a 

 month and secretes nectar constantly. According to J. J. Wilder 

 these flowers are seldom visited by bees. 



3 To Robertson's hypothesis that, in the remote past, oligo- 

 tropism arose through the competition of the long-tongued 

 pygidial bees with the Bombidae, and of the Andrenidae with 

 the Halictidae, Lovell replies : ' This highly imaginative suppo- 

 sition cannot be supported by historical data, and would appear 

 to be neither probable nor necessary." The polytropism of 

 Halictus is due to its peculiar economy. The impregnated 

 females hibernate and appear the following spring. The new 

 generation flies during the latter part of the season. " This 

 economy has no special advantage, for Halictus is greatly sur- 

 passed by Andrena in both species and individuals; while Sphe- 

 codes, which has essentially the same economy as Halictus, is 

 represented by comparatively few species and individuals. 



It is an advantage for a social bee to maintain its organiza- 

 tion throughout the season; but for a solitary insect it is desir- 

 able that it mate and deposit its eggs as soon as possible. The 

 longer the female flies before this happens the greater the prob- 

 ability that she will be destroyed by some one of many causes. 

 * * * Since many polytropic bees have either a short term of 

 flight, or one which does not exceed a hundred days, it is clear 

 that a shorter term of flight is not necessarily correlated with 

 oligotropism." 



4. If severe competition did exist among solitary bees the 



