112 
Psyche 
[June 
PHENOLOGY OF OLIGOLECTIC BEES AND 
FAVORITE FLOWERS 
By Charles Robertson 
Carlinville, Illinois 
Authors who have discussed this subject have made no 
systematic phenological observations on bees or on flowers. 
Referring to the supposed short flight of oligoleges, one 
says : “Some claim this is so because they are small .Robert- 
son explains it by saying that the short flight is the result 
of the visiting of the few closely allied genera of plants.” 
“Both opinions are probably right.” Oligolectic bees are not 
small and their flight averages only 11.8 days shorter than 
their related polyleges (4, 422). In 2, 71, it is stated that 
these bees are no smaller than their relatives and the per- 
centage of small bees is no greater than among the poly- 
tropes (polyleges). Of local oligoleges, 38 per cent, while 
of the polyleges 37 per cent, are large. There is no need to 
explain something which is not a fact. 
Bees with short flight. — Since the female bees do the 
pollen-collecting, the statements here relate to them. In 1, 
30, it is shown that the females of 33 Andrenidse, both poly- 
lectic and oligolectic, average 48 days and complete their 
flight in 120 days, March 17- July 14. It was argued that it 
was advantageous for some of these short-flying bees to fall 
into 11 sets with non-competitive pollen-collecting habits. 
Polylectic Andrenidse average only 7.7 days longer than the 
oligoleges (4, 427). Oligolectic bees resemble their relatives 
in time even more than they resemble the plants on which 
they depend (3, 108). The percentages of bees flying simul- 
taneously, May-September, are from 45.9 to 47.2 (5, 522). 
Short flights make it possible for the bees to be distributed 
so that not more than 47.2 per cent are flying at the same 
time (3, 107). This, I think, shows the principal advantages 
of a short flight. 
