38 INTERRELATIONS OF PLANTS AND ANIMALS 



The pronuba moth within the 

 yucca flower. 



botanic gardens). In this flower the stigmatic surface is above the 

 anther, and the pollen is sticky and cannot be transferred except 

 by insect aid. This is accomplished in a remarkable manner. A 

 little moth, called the pro'nuha, after gathering pollen from an 

 anther, flies away with this load to another flower, there de- 

 posits an egg in the ovary of the pistil, 

 and then rubs its load of pollen over 

 the stigma of the flower. When the 

 egg hatches, the caterpillar feeds on 

 some of the young seeds which have 

 , ^ grown because of the pollen placed on 



/V^ y the stigma by the mother. Later it 



bores out of the seed pod and escapes 

 to the ground, leaving the plant to de- 

 velop the remaining seeds without 

 further molestation. 



The fig insect {Blastophaga gros- 

 sorum) is another member of the insect 

 tribe that is of considerable economic importance. The fertili- 

 zation of the flowers of the fig tree is brought about by a wasp 

 which bores into the young fruit. By importing the wasps to 

 California it was made possible to grow figs where for many years 

 it was believed that the climate prevented them from ripening. 



Other Visitors to 

 Flowers. — Among other 

 useful pollen carriers for 

 flowers are butterflies. 

 Projecting from each side 

 of the head of a butterfly 

 or a moth is a fluffy 

 structure, called thepaZp. 

 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 of a butterfly also carry pollen. 



Humming birds, like bees, cross-pollinate some 

 flowers while seeking nectar and insects. 



