96 INSTINCTS 



activities as when full grown. The inexplicable 

 acuteness of the Scolia wasp and its larva has 

 been already mentioned. The life histories of the 

 Yucca moth and the Sitaris beetle are not less 

 astonishing. The former takes a lump of pollen 

 from the anthers of one Yucca flower, lays its eggs 

 in the ovary of another flower, and, before flying 

 off, fertilizes this flower by depositing the lump of 

 pollen upon its stigma. The larvae feed upon the 

 ovules in the ovary, and would be short of 

 nourishment unless these were fertilized and grew 

 to maturity. But they do not consume all the 

 ovules : some are spared and form seed to carry 

 on the life of the plant in the next generation. 

 The transfer of pollen from one flower to another is, 

 then, necessary for the life both of the larvae and 

 the plant. But we are quite unable to understand 

 how these two distinct necessities come to be 

 linked through the impulses of the moth. The 

 Sitaris beetle lays its eggs at the mouth of the 

 burrow of the Anthophora mason bee : its young 

 are active little creatures with prehensile claws, 

 and leap on to the drones as they pass out of the 

 burrow on their nuptial flight. They transfer 

 themselves to the females during the process of 

 mating, are carried by the females to the nest, 

 and transfer themselves again on to the eggs, when 

 laid, living upon them and upon the store of 

 honey until the time comes for their metamor- 

 phosis into adult beetles. The larvae are endowed 

 with special organs and special impulses for their 

 threefold migration, the object of which is to 

 enable them to live, in a most complicated 

 fashion, upon the lives of others. 



Directive instinct is absolutely unreasoning, and 

 will accept no guidance from inference. A mud- 

 wasp (Pelopoeus) will continue to provision its 

 nest-cell for its young after the egg which it has 



