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 
Bre. 252: 
Bumble bee (Bombus) entering flower of blue-fiag (Jris 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 
