70 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. 
sinillima; 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- 
pactus, 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. Gaz. 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, 7. 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 
