Ch. VIII.] IXSTIXCT AT FAULT. 135 



They also build tlieir pendant nests in the orange and 

 lime trees, and it is not always safe to gather the fruit. 

 Fortunately they are heavy flyers, and can often be 

 struck down or evaded in their attacks. They do good 

 where there are gardens, as they feed their young on 

 caterpillars, and are continually hunting for them. 

 Another species, banded brown and yellow (Polistes 

 carnifcx), has similar habits, but is not so common. 

 Bates, in his account of the habits of the sand-wasps at 

 Santarem, on the Amazon, gives an interesting account 

 of the way in which they took a few turns in the air 

 around the hole they had made in the sand before 

 leaving to seek for flies in the forest, apparently to mark 

 well the position of the burrow, so that on their return 

 they might find it without difficulty. He remarks that 

 this precaution would be said to be instinctive, but 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.* I had an 

 opportunity of confirming his account of the proceedings 

 of wasps when quitting a locality to which they wished 

 to return, in all but their unerring certainty. I could not 

 help noting how similar they were to the way in which 

 a man would act who wished to return to some spot not 

 easily found out, and with which he was not previously 

 acquainted. A specimen of the Polistes carnifex was 

 hunting about for caterpillars in my garden. I found 

 one about an inch long, and held it out towards it on the 

 point of a stick. It seized it immediately, and com- 

 menced biting it from head to tail, soon reducing the soft 

 body to a mass of pulp. It rolled up about one-half of 

 * " Naturalist on the Amazon," p. 222. 



