168 THE STUDY OF ANIMAL LIFE CHAP. 



her head. She flies to another flower, pierces the pistil 

 with her ovipositor, lays her eggs among the ovules, and 

 then places the fertilising pollen-pellet in the funnel- 

 shaped opening of the stigma. Without the pollen thus 

 brought by the moth to the pistil the ovules would not 

 develop. The larvae of the moth eat a share of the 

 developing ovules, but not more than about half are 

 required. In referring to this extraordinary case, Prof. 

 Lloyd Morgan writes : 



" These marvellously adaptive instinctive activities of the Yucca 

 Moth are performed but once in her life, and that without instruc- 

 tion, with no opportunities of learning by imitation, and, appar- 

 ently, without prevision of what will be the outcome of her behaviour, 

 for she has no experience of the subsequent fate of the eggs she lays, 

 and cannot be credited with any knowledge of the effect of the 

 pollen upon the ovules. The activities also illustrate what is by no 

 means infrequent in the more complex instincts, namely, the serial 

 nature of the adaptation. There is a sequence of activities, and 

 the whole sequence is adaptive in its nature." 



What are the general characteristics of instinctive 

 behaviour as we see it in animals like ants, bees, and 

 wasps, which belong to what Sir Ray Lankester has 

 called the little-brain type, in contrast to animals like 

 birds and mammals which belong to the big-brain type ? 



(1) Instinctive behaviour in its typical expression is 

 specific or particulate. The garden-spider's web is not 

 like the hedge-spider's web ; the nest of one wild bee is 

 not like another's ; each species of wasp has its own 

 way of dealing with its victims. 



(2) The routine of instinctive behaviour is gone through 

 with a considerable degree of perfection the very first 

 time, and while it may be improved by practice, it cer- 

 tainly docs not require learning or experimenting. It 

 depends upon an hereditary predisposition of the nervous 

 system. It " just comes ' when the creature meets the 

 appropriate stimulation. 



(3) The capacity for a particular piece of instinctive 

 behaviour is shared with approximate equality by all 

 like members of the species. All the female spiders of a 

 given species make an equally fine web ; all the males an 



