112 The American Naturalist. [February, 
of their groups, having no doubt shifted to: take a more favor- 
able position under the competition of other flowers. Thus 
the earliest member of the mint family (Fig. 13, Plate VIII), is a 
bumble-bee flower, and some of the earliest of the figwort 
family (Fig. 19, Plate VIII) are adapted to these insects. The 
larkspur itself is anticipated by four bumble-bee flowers be- 
longing to more highly specialized families. We would, there- 
fore, expect to find bumble-bee flowers at favorable points of 
origin or shifted to favorable positions, and the whole group of 
flowers so disposed as to share the services of these long- 
tongues with as little interference among themselves as pos- 
sible. Of the sixty-four species on which the curve (Fig. 41, 
Plate X) is based the different forms succeed one another from 
the first of April until the middle of October in such a way 
that not more than twenty-five species are in bloom at the 
same time. Twenty-six have completed their flowering by 
the last of June. We will compare this curve with that for 
bumble-bees. The first bumble-bees which fly in the spring 
are the females; in May, June and July the workers appear ; 
and finally in July, the males. The workers are more 
abundant and even more industrious than the females, and 
the males are frequently quite numerous and efficient flower 
visitors. In making a curve for bumble-bees (Fig. 30, Plate IX), 
therefore, I have introduced each sex as an elementso that the 
maximum coincides with the flight of the three forms, and I 
think this is the only way to indicate in a curve the function 
of the genus as a pollinating agency. Now if we compare the 
curve for bumble-bees (Fig. 30, Plate IX) with the curve for the 
bumble-bee flowers (Fig. 41, Plate X) we find a well marked 
coincidence. 
The curve for the other flowers adapted to the higher bees 
(Fig. 44, Plate X) indicates a more pronounced maximum, evi- 
dently because the higher bees in general show a more marked 
preponderance in summer. Of sixty-nine species on which 
the curve is based, thirty are in bloom simultaneously at the 
maximum point. 
Now as observed above, the lower bees (Andrenidae, Fig. 26 
PlateIX) prefer erect simple flowers with easily accessible nectar 
