218 Mr. A. R. Wallace's Note 



XVII. Note on the Habits of Scolytidae and Bostrichidse. 

 By Alfred R. Wallace, Esq., Corr. Memb. 

 Ent. Soc. 



[Read December 5th, 1859.] 



There seems to be much difference of opinion among Entomo- 

 logists as to whether the little wood-boring beetles of the families 

 Scolytidce and Bostrichidcc do really injure and destroy trees, or 

 whether they only attack such as are already diseased and par- 

 tially dead from some other cause. Believing that the habits of 

 the exotic species will help to clear up this question, I beg to 

 offer a few observations on those which I have met with in the 

 Malayan Archipelago, 



The species of these islands are not generally larger than those 

 of Europe, a great number being about a line in length, and the 

 largest only five lines. They appear to be very nuinerous in 

 species, about twenty generally occurring in each locality I have 

 visited, while at Dorey, in New Guinea, I captured no less than 

 thirty-eight distinct species, about equally divided between the 

 two families. I have taken about half of these in the house, 

 whenever I have inhabited one newly built in the forest, as at 

 Macassar and Dorey, and the rest under bark in various stages of 

 decay, or flying about fallen trees. Every species has been taken 

 invariably on or in the vicinity of cut or dead trees. Never in 

 the course of five years, almost daily spent in the forests, have I 

 seen a single individual of either of these families attacking 

 healthy living trees, or have found any traces of them having 

 bored into such trees. 



On the other hand, whenever a tree falls or is cut down, they 

 are the first to attack it. In about four or five days dozens of 

 minute holes may be seen on the trunk and branches, from each 

 of which a little fine wood-dust falls down, and on carefully 

 watching we may generally discover some of the insects pushing 

 out the dust with the truncate extremity of the elytra. In some 

 trees I have detected two or three species at work, in others only 

 one. Some of the smallest attack cut and drying bamboos, 

 others bore into hard dry boleti. No doubt, however, there are 

 species that attack several trees indiscriminately. I had cut down 



