260 



ENTOMOLOGY 



Cross fertilization is actually a necessity for the continued 

 vigor and fertility of flowering plants, and while some of them 

 are adapted for cross pollination by wind or water, the major- 

 ity of flowering plants exhibit profound modifications of floral 

 structure for compelling insects (and a few other animals, as 

 birds or snails) to carry pollen from one flower to another. In 

 general, the conspicuous colors of flowers are for the purpose 



FIG. 252. 



Bumble bee (Bombus) entering flower of blue-flag (Iris versicolor). Slightly 



reduced. 



of attracting insects, as are also the odors of flowers. Night- 

 blooming flowers are often white or yellow and as a rule 

 strongly scented. Colors and odors, however, are simply 

 indications to insects that edible nectar or pollen is at hand. 

 Such is the usual statement, and it is indeed probable that 



