7<3 ENTOMOLOGICAL NEWS. [Feb., '14 



compositarum, M. asteris; Helianthoideae: Sayapis pollicaris, 

 pugnata, Pterandrena aliciae, pulchella, rudbeckiae, Pseudo- 

 panurgus albitarsis, rudbeckiae, labrosus, labrosiformis, ru- 

 gosus, M. illinoensis; Asteroideae and Helenioideae: M. 

 simillima ; Asteroideae and Helianthoideae : Colletes ameri- 

 canus, Pseudopanurgus asteris, solidaginis, Perdita 8-maculata, 

 M. autumnalis ; Helianthoideae and Asteroideae : Ashmeadiella 

 bucconis, Megachile 6-dentata, Pterandrena helianthi, Calliop- 

 sis coloradensis, M. agilis ; Helianthoideae and Cynarioideae : 

 Sayapis pugnata, M. coloradensis; Three tribes: Colletes com- 

 pact us, Gnathosmia georgica, M. trinodis, Sayapis sayi ; Four 

 tribes: M. boltoniae. 



Lovell says : "How has the oligotropic habit originated ? 

 Mr. Robertson believes that it is the result of an effort on the 

 part of the different species to avoid competition. I hold that 

 it has arisen because of the advantage gained coupled with a 

 short term of flight." He also says : "Accessory factors are 

 small size, time of flight, weak flight, vicinity of nests, and 

 the number of bees." 



In the Bot. Gas. 28: 29, 30, 1899, I have recognized a short 

 flight as an important condition of oligotropy and have prac- 

 tically excluded bees of long flight from the discussion. The 

 use of the words "an effort" in every reference to my views 

 is not justified. I have never used that expression or any words 

 implying that idea. My view is that the bee fauna is all that 

 the flora will support, that there is constant competition be- 

 tween the bees, and that natural selection favors those which 

 are the most diversified, i. e., the least competitive in their 

 food habits. 



Compared with bees which fly all season the oligotropes 

 have a short flight, but that they, as compared with their rela- 

 tives, originally had a short flight there is no evidence. And 

 the general statement that they have a short flight is mislead- 

 ing. Compare : 



Less than 51 days 51-100 days Over 100 days 

 Oligotropes 30 36 7 



Polytropes 18 39 9 



The average flight is shorter and there are more of them 



