276 THE ARU ISLANDS. [chap, xxxii. 



&c.), 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 glueing 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 sufficient instinctive 

 knowledge of which trees were suitable, and which 

 destructive to them. If, as is very probable, these trees 

 have an attractive odour to certain species of borers, it 

 might very likely lead to their becoming extinct ; while 

 other species, to whom the same odour was disagreeable, 

 and who therefore avoided the dangerous trees, would sur- 

 vive, and would be credited by us with an instinct, whereas 

 they would really be guided by a simple sensation. 



Those curious little beetles, tlie Brenthidae, were very 

 abundant in Aru. The females have a pointed rostrum, 

 with which they bore deep holes in the bark of dead trees, 

 often burying the rostrum up to the eyes, and in these 

 holes deposit their eggs. The males are larger, and have 

 the rostrum dilated at the end, and sometimes terminating 

 in a good-sized pair of jaws. I once saw two males fight- 

 ing together ; each had a fore-leg laid across the neck of 

 the other, and the rostrum bent quite in an attitude of 

 defiance, and looking most ridiculous. Another time, two 



