204 OUR INSECT FRIENDS AND FOES 



other hand, it is ascertained beyond a doubt that 

 the grub of the moth in question lives exclusively 

 on the young seeds of these species of Yucca, 

 so that one is forced to the conclusion that the 

 moth stuffs the pollen into the stigma in order 

 that its grubs may be supplied with the nutri- 

 ment requisite for the preservation of the species 

 nutriment which would not be forthcoming 

 unless the ovules were fertilized. It must be 

 observed that the grubs of Pronuba yuccasella 

 do not eat up all the developing seeds of the 

 ovary in which the moth lays her eggs. There 

 are about two hundred ovules in each ovary. 

 Even if half or two-thirds of them are consumed, 

 there is still a sufficient number of uninjured seeds 

 left to be scattered abroad when they have reached 

 maturity, whereas, without the intervention of 

 the moth, not a single seed capable of germina- 

 tion would be produced. 



" Still more remarkable than the relation 

 between the genus Yucca and its companion 

 moth is that existing between Fig-trees and 

 certain small wasps of the group of the Chalci- 

 didce. To understand the relation clearly, it is 

 first of all necessary to examine the construction 

 of the inflorescence in the Fig. Looking at a fig 

 that has been cut open lengthwise, it is observed 

 that it is not a simple flower, but rather a whole 

 collection of flowers inclosed in an urn or pear- 

 shaped receptacle. These pear-shaped shoots 

 are in reality hollow inflorescences bearing 

 numerous flowers on their inner walls. Each 

 fig is termed a 'synconium.' The orifice of the 

 urn is very small, and is further straitened by 



