454 THE ANIMALS AND MAN 



the conifers, the grasses and many other plants mostly 

 without sepals and petals, is the production of vast quantities 

 of light loose pollen grains to be distributed by the winds. 

 "Sulphur rains" that come sometimes at the pollen ripening 

 time of pinetrees are simply showers of wind-blown yellow 

 pollen from the forests. With nectar and pollen ready 

 for use the plant has yet to advertise its sweets to the insects, 

 and for this brilliant colors and attractive odors are relied on. 

 An odor attractive to insects is not always pleasing to us, for 

 the Araceas, some Trilliums and others have a carrion-like 

 odor "combined with dull colors often marked with livid 

 blotches or veins like dead animal bodies, and these flowers 

 attract flesh-flies and carrion-beetles which are the pollinat- 

 ing agents." The simpler insect-visited flowers, such as 

 those of the apple, cherry, wild rose, ranunculus, etc., are 

 mostly wide open and accessible to a large variety of insect 

 visitors. They are all abundant pollen providers and some 

 secrete nectar which is easily got at. But to get either 

 nectar or pollen the insects have to scramble over and among 

 the many crowded stamens of the center, dusting themselves 

 well during the process with pollen, which is carried on to 

 the next flower visited and there probably rubbed off on to 

 the stigma. To such simple flowers, and to others like 

 them, as the Umbelliferse and the numerous Compositse, 

 many kinds of insects may come. For example, Robertson 

 found 275 different insect species visiting an UmbeUifer 

 in three months in Illinois, and 146 kinds visiting a golden 

 rod in II days. 



With the flowers of tubular corolla the nectar can be got 

 at only by insects especially provided with long tongues, 

 such as bees and some flies, moths and butterflies. 

 The deeper kinds of flowers are mostly visited by insects 

 with especially long proboscides. The common jimson- 

 weed, Datura stramonium, is, as Stevens says, an excellent 

 example of this. "The corolla is about five centimeters 



