INSECTS AND FLOWERS 459 



nated (with pollen brought from other flowers) by the enter- 

 ing insects, wither, a drop of nectar is secreted for the 

 benefit of the captured insects, and the anthers mature, 

 exposing their ripe pollen-grains. The hairs in the throat 

 of the flower gradually shrivel up and release the insects 

 which are now well showered with pollen falling on them 

 from the anthers above. Visiting another Arum-flower, 

 they hardly fail to rub off some of this pollen on the mature 

 stigmas. Sometimes more than a hundred small flies will 

 be found imprisoned in a single Arum. 



Classic examples of apparently the wildest vagaries in 

 flower structure are those presented by the orchids. But 

 Darwin's fine work revealed the method in all this floral mad- 

 ness. Orchids are pollinated almost exclusively by insects, 

 and the extravagant shapes and color-patterns are all means 

 for accomplishing cross-pollination. Any one interested at 

 all in the interrelation between flowers and insects should 

 read Darwin's account of the orchids and their insect visitors, 

 in his book "On the Fertilization of Orchids by 

 Insects." 



The above few examples of the interrelations between 

 flowers and insects are not exceptional cases. Indeed, this 

 state of affairs is the rule throughout the families of flower- 

 ing plants. The absence of it is the exception. Cross- 

 pollination by insects is far more abundant than self-pollin- 

 ation. 



It is of distinct interest to note that no plants of colored 

 flower-parts existed (in geologic time) before the time of 

 winged insects. The insects which we know today as the 

 pollen- and nectar-feeders, hence flower visitors, began to 

 be abundant in the world coincidentally with or a little in 

 advance of the flowering plants. Mutually helpful and 

 mutually adapting themselves to each other, the flies, bees, 

 moths, and butterflies, on the animal side and all those plants 

 with flowers of varied shapes, color, and patterns, on the 



