262 INSECT MECHANICS 



dog. In other words, it was a pure fluke ; but it passed 

 into experience, for it happened more than once. Dogs, 

 of course, are exceedingly susceptible of experience ; after 

 each successive repetition there was less poking of this 

 one's head into wrong openings, till at last he ' learnt to 

 go straight and without hesitation to the right spot.' 

 Yet the same dog ' seemed to be incapable of perceiving 

 the nature of the difficulty which vertical iron railings 

 presented to his passage with a stick in his mouth.' 

 When sent after a stick into a field through railings six 

 inches apart he dashed back with it, always held by the 

 middle, and found his return hopelessly barred by the 

 ends catching in the railings. Nor, although the experi- 

 ments were continued through two summers, did this 

 highly intelligent animal ever change his behaviour 

 with the stick, or learn what a moment's real reflection 

 would have taught him to pass it through the railings 

 lengthwise. 



XLVII 



Occasionally the close observer comes across startling 

 insect manifestations of intelligence in animals very 

 Mechanics f ar i n f er i or to dogs in the scale. The infinite 

 varieties of device and function in insects are usually 

 affected by means of highly specialised organs adapted for 

 definite purposes. But in the course of his most interest- 

 ing studies upon the habits of the solitary wasps, Dr. 

 Peckham was witness of the behaviour of one of the 

 genus Ammophila which it is scarcely possible to account 

 for by intelligence profiting by chance experience, as in 

 the case of the fox-terrier lifting the latch of the gate. 

 The deliberate use of a tool is generally supposed to 



