34 SANTAREM. Chap. I. ^ 
of at least half a mile to procure the kind of fly, the 
Motuca (Hadaiis lepidotus), with which it provision^ its 
cell. I often noticed it to take a few turns in the air 
round the place before starting ; on its return it made 
without hesitation straight for the closed mouth of the 
mine. I was convinced that the insects noted the bear- 
ings of their nests and the direction they took in flying 
from them. The proceeding in this and similar cases (I 
have read of something analogous having been noticed in 
hive bees) seems to be a mental act of the same nature 
as that which takes place in ourselves when recognising 
a locality. The senses, however, must be immeasur- 
ably more keen and the mental operation much more 
certain in them than it is in man ; for to my eye there 
was absolutely no land-mark on the even surface of 
sand which could serve as guide, and th e borders of the 
forest were not nearer than half a mile. The action 
of the wasp would be said to be instinctive ; but it 
seems plain that the instinct is no mysterious and unin- 
telligible agent, but a mental process in each individual, 
differing from the same in man only by its unerring 
certainty. The mind of the insect appears to be so con- 
stituted that the impression of external objects or the 
want felt, causes it to act with a precision which seems 
to us like that of a machine constructed to move in a 
certain given way. I have noticed in Indian boys a 
sense of locality almost as keen as that possessed by 
the sand-wasp. An old Portuguese and myself, accom- 
panied by a young lad about ten years of age, were 
once lost in the forest in a most solitary place on the 
banks of the main river. Our case seemed hopeless, 
