THE FLOWER AND THE BEE 



is a monotropic bee. When a species of bee restricts its visits 

 chiefly to one kind of flower it is termed a monotropic bee; or 

 to a few allied kinds of flowers an oligotropic bee; but if it visits 

 many flowers a polytropic bee. These terms were first pro- 

 posed by Loew, and signify: adapted to one, few, or many 

 flowers. 



It is impossible not to feel some curiosity as to why this little 

 bee restricts its visits to the inflorescence of the pickerel-weed. 

 Notice that it flies only at the season of the year when this 

 aquatic plant is in bloom, and that it finds within the perianth 

 both food and shelter. Very likely its nests are built not far 

 away. The flowers of the pickerel-weed strongly attract in- 

 sects by their great numbers, bright hues, pleasant fragrance 

 and abundant nectar and pollen, and consequently are sought 

 out by many bees, flies, and butterflies. (Fig. 53.) Bumble- 

 bees especially delight in these blossoms, which they visit with 

 astonishing rapidity Bombus vagans making about 70 visits per 

 minute. On the middle lobe of the upper lip there are two 

 bright-yellow spots, which tell of the presence and guide to 

 the exact location of the nectar concealed within the tube 

 of the perianth. When the pickerel-weed bee makes its appear- 

 ance, about the middle of July, there is no other flower in south- 

 ern Maine which can offer it so many inducements as the pick- 

 erel-weed. But let us look further and see if there are any 

 other bees which behave in a similar manner. 



In the quiet bays of the river, floating upon the surface of 

 the water, bloom the yellow water-lilies (Nymphcpa ad vena). 

 (Fig. 54.) 



"Again the wild cow-lily floats 

 Her golden-freighted, tented boats, 

 O'ershadowed by the whispering reed, 

 And purple plumes of pickerel-weed." 



106 



