INTERRELATIONS OF PLANTS AND ANIMALS 43 



nating the pistil 

 of the yucca. 



pillars eat some of the devel 

 oping seeds and later bore 

 out of the seed pod and 

 escape to the ground, leav 

 ing the plant to develop 

 the remaining seeds without 

 further molestation. 



The fig insect (Blastophaga 

 grossorum) is another mem 

 ber of the insect tribe that 

 is of considerable economic 

 importance. It is only in The pronuba polli 

 recent years that the fruit 

 growers of California have 

 discovered that the fertilization of the female 



Pod of yucca showing . 



where the young pro- flowers is brought about by a gallfly which 



nubas escaped. bores into the young fruit. By importing 



the gallflies it has been possible to grow figs where for many 

 years it was believed that the climate prevented figs from 

 ripening. 



Other Flower Visitors. Other insects besides those already 

 mentioned are pollen carriers for flowers. Among the most use 

 ful are moths and butterflies. Projecting from each side of the 

 head of a butterfly is a fluffy structure, the palp. This collects 

 and carries a large amount 

 of pollen, which is deposited 

 upon the stigmas of other 

 flowers when the butterfly 

 pushes its head down into 

 the flower tube after nectar. 

 The scales and hairs on the 

 wings, legs, and body also 

 carry pollen. 



Flies and some other in 

 sects are agents in cross- 



pollination. Humming birds A humming Mrd about to crosa . pollinate 

 are also active agents in a lily. 



