196 SANTAREM. Cuap. VIII. 
the insect has to make a journey of at least half a mile to procure the 
kind of fly, the Mottica (Hadaiis lepidotus), with which it provisions 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 
bearings 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 recog- 
nising a locality. The senses, however, must be immeasurably more 
keen, and the mental operation much more certain, in them than they 
are in man; for to my eye there was absolutely no landmark on the 
even surface of sand which could serve as guide, and the 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 unintelligible 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 constituted 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, accompanied 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, and it did not for some time occur to 
us to consult our little companion, who had been playing with his bow 
and arrow all the way whilst we were hunting, apparently taking no note 
of the route. When asked, however, he pointed out, in a moment, the 
right direction of our canoe. He could not explain how he knew; I 
believe he had noted the course we had taken almost unconsciously. 
The sense of locality in his case seemed instinctive. 
The Monedula signata is a good friend to traveilers in those parts of 
the Amazons which are infested with the blood-thirsty Mottica. I first 
noticed its habit of preying on this fly one day when we landed to make 
our fire and dine on the borders of the forest adjoining a sandbank. 
The insect is as large as a hornet, and has a most waspish appearance. 
I was rather startled when one out of the flock which was hovering about 
us flew straight at my face: it had espied a Mottica on my neck, and 
was thus pouncing upon it. It seizes the fly not with its mandibles, but 
with its fore and middle feet, and carries it off tightly held to its breast. 
Wherever the traveller lands in the Upper Amazons in the neighbour- 
hood of a sandbank, he is sure to be attended by one or more of these 
useful vermin-killers. 
The bay of Mapirf was the limit of my day excursions by the river- 
side, to the west of Santarem. A person may travel, however, on foot, 
as Indians frequently do, in the dry season for fifty or sixty miles along 
the broad clean sandy beaches of the Tapajos. The only obstacles are 
the rivulets, most of which are fordable when the waters are low. To 
the east my rambles extended to the banks of the Mahica inlet. This 
