IO6 KNTOMOLOGTCAL NEWS. [March, '13 



persons do suppose. Oligotropism could not have been self- 

 evident to Hermann Muller or he would not have written 

 (Fertilization of P J ants, p. 570) : "In general anthophilous 

 insects are not limited by hereditary instinct to certain flowers, 

 but they wander about getting their food on whatever flowers 

 they find it." etc. 



In the paragraph beginning with the sentence, "The oli- 

 gotropic habit is not beneficial to flowers, it concerns the bees 

 alone," oligotropism is stated to have arisen independently of 

 any benefit received by the flowers and solely because it is 

 an advantage to the bees. It would seem that no one could 

 be misled by the paragraph as a whole, except perhaps an over- 

 willing critic. I can hardly believe that Robertson supposed 

 that I intended to deny the value of "flower fidelity" to flowers. 

 Personally, I believe that flower fidelity on the part of bees is 

 an advantage to flowers, as I stated later in my article and as 

 Robertson noticed ; though the advantages of cross-pollination 

 are questioned by some ecologists. The writer distinguishes 

 between oligotropism and flower fidelity. The oligotropic 

 habit is flower fidelity carried to the extreme. Polytropic bees 

 also possess flower fidelity. It would not be an advantage to a 

 flora for all the bees to be oligotropic, since then many ento- 

 mophilous flowers would not be visited by these most im- 

 portant agents in pollination. The time of flight of many 

 polytropic bees would necessarily be greatly reduced, which 

 would clearly be a great disadvantage. I know of no native 

 flower which is wholly dependent for pollination on an oli- 

 gotropic bee ; usually the flowers are visited by many other 

 bees and the oligotropic bee may be comparatively rare and 

 unimportant. Andrena solidaginis is so rare in this locality 

 as to be of no significance in the pollination of Solidago. It 

 is sufficient if a flower is effectively pollinated, and repeated 

 visits may be and often are useless. Therefore the ento- 

 mophilous flora of a region, as a whole, is not better pollinated 

 because a part of the bees are oligotropic than it would be if 

 they were all polytropic. 



How has the oligotropic habit originated? Mr. Robertson 



