S46 THE ORIGIN OF SPECIES 



CHAPTER VIII 



INSTINCT 



Instincts comparable with habits, but different in their origin — Instincts 

 graduated — Aphides and ants — Instincts variable — Domestic instincts, 

 their origin — Natural instincts of the cuckoo, molothrus, ostrich, and 

 parasitic bees — Slave-making ants — Hive-bee, its cell-making instinct — 

 Changes of instinct and structure not necessarily simultaneous — Diffi- 

 culties of the theory of the Natural Selection of instincts — Neuter or 

 sterile insects — Summary 



M 



ANY instincts are so wonderful that their devel- 

 opment will probably appear to the reader a dif- 

 ficulty sufficient to overthrow my whole theory. 

 I may here premise, that I have nothing to do with the 

 origin of the mental powers, any more than I have with 

 that of life itself. We are concerned only with the 

 diversities of instinct and of the other mental faculties 

 in animals of the same class. 



I will not attempt any definition of instinct. It would 

 be easy to show that several distinct mental actions are 

 commonly embraced by this term; but every one under- 

 stands what is meant, when it is said that instinct impels 

 the cuckoo to migrate and to lay her eggs in other birds' 

 nests. An action, which we ourselves require experience 

 to enable us to perform, when performed by an animal, . 

 more especially by a very young one, without experience, l| 

 and when performed by many individuals in the same 

 way, without their knowing for what purpose it is per- 



