Failure of Instinct. 481 



of that system. It must be remembered too that our com- 

 merce is not a purely natural growth. It has been ever fos- 

 tered by the legislature, and forced to an unnatural luxuri- 

 ance by the protection of our fleets and armies. The wisdom 

 and the justice of this policy have been already doubted. So 

 soon, therefore, as it is seen that the further extension of our 

 manufactures and commerce would be an evil, the remedy is 

 not far to seek. 



After six weeks' confinement to the house I was at length 

 well, and could resume my daily walks in the forest. I did 

 not, however, find it so productive as when I had first arrived 

 at Dobbo. There was a damp stagnation about the paths, 

 and insects were very scarc6. In some of my best collecting 

 places I now found a mass of rotting wood, mingled with 

 young shoots, and overgrown with climbers, yet I always 

 managed to add something daily to my extensive collections, 

 I one day met with a curious example of failure of instinct, 

 which, by showing it to be fallible, renders it very doubtful 

 whether it is any thing more than hereditary habit, dependent 

 on delicate modifications of sensation. Some sailors cut 

 down a good-sized tree, and, as is always my practice, I visit- 

 ed it daily for some time in search of insects. Among other 

 beetles came swarms of the little cylindrical wood-borers 

 (Platypus, Tesserocerus, etc.) and commenced making holes 

 in the bark. After a day or two I was surprised to find 

 hundreds of them sticking in the holes they had bored, and 

 on examination discovered that the milky sap of the tree was 

 of the nature of gutta-percha, hardening rapidly on exposure 

 to the air, and gluing the little animals in self-dug graves. 

 The habit of boring holes in trees in which to deposit their 

 eggs, was not accompanied by a sufiicient instinctive knowl- 

 edge of which trees were suitable, and which destructive to 

 them. If, as is very probable, these trees have an attract- 

 ive odor to certain species of borers, it might very likely lead 

 to their becoming extinct ; while other species, to whom the 

 same odor was disagreeable, and who therefore avoided the 

 dangerous trees, would survive, and would be credited by 

 us with an instinct, whereas they would really be guided by 

 a simple sensation. 



Hh 



