30 

 require all of the ovules. Shelter is another reason why 

 insects go to flowers, as in Indian Turnip, S kunk Cabbage, 



e. 



The structures that attract insects 



Modes of Attraction. ,^ . , ■ j- i , 



are, (1) large size. lorm, color, and 



odor of flowers, (2) food (pollen, nectar), material for the 



construction of nests, shelter as in Arum and Indian Turnip, 



places where the eggs hatch and later the larvae feed on the 



ovules, as in Yucca, etc. 



Certain insects are excluded because of the color and 

 odor of flowers. 



Herman Mueller classified flowers, with reference to 

 their insect visitors, as follows: 



Polieti Flowers. Furnish insects with pollen only. 

 Poppy, etc. 



Flowers with Exposed Nectaries. Adapted to various 

 kinds of insects, nectary shallow, not highly colored, yellow, 

 white, etc., — Galium, Elder. 



Flowers with Half Hiddeti Nectaries. Honey visible 

 during warm sunshine, u umber of visitors reduced, long 

 tongued insects have increased, — Crucifera, Ranunculus, 

 Fragaria. 



Flowers with Concealed Nectaries. Special adaptation 

 to a particular class of insects not developed. Short 

 tongued insects debarred, as in Mentha, Oxalis, Geranium. 



Flowers in Heads, Nectar Concealed. Flowers rendered 

 attractive because of the massing, — Composites, Scabiosa. 



Bee Flowers. Adopted to Hymenoptera. Short 

 tongued insects excluded, — Gentian, Digitalis, Columbine. 



Lepidoptera Flowers. Nectar deep seated, in tubes, 

 spurs can be reached only by the long tongues of these 

 insects. Flowers fragrant. Diurnal flowers as Silene and 



