202 

 XOTES OX FOREST IX SECTS ^ 



The Hawaiian forests are inhabited by a very large nnniber of 

 species of insects, most of which are so hidden and of such in- 

 conspicuous appearance that the forest region appears to be ten- 

 anted by very few kinds to people who have not paid particular 

 attention to the habits of the creatures. Very few of the native 

 insects do such damage as to be considered injurious, and at the 

 present time very few imported species have caused any consid- 

 erable destruction of forest trees. Consequently it may be said 

 that the Hawaiian forests are probably more free from injurious 

 insects than those of most, if not any, other parts of the world. 



It is in many cases extremely difficult even for a trained en- 

 tomologist to decide on the exact status of an insect found in 

 connection with dead, dying or diseased timber. Such timber 

 is always very attractive to many kinds of creatures, and the out- 

 sider observing these to be abundant, almost invariably attributes 

 to them damage which has been brought about by quite different 

 causes. Many of the insects supposed to be injurious in such 

 cases are really highly beneficial, for they perforate and break up 

 the dead wood, allowing water to penetrate to the heart of the 

 timber and hasten decay, so that even a hard-wooded tree may 

 be rapidly converted into humus. Further, in the case of old and 

 diseased trees, the attacks of insects, that are partial to these, 

 hasten the death of the tree and make room for younger and 

 more healthy growth. There are, however, cases where, owing 

 to various causes, a temporarily unhealthy condition of the forest 

 is induced, and trees so affected are readily attacked by a number 

 of species of insects. This may result in the actual death of 

 trees, which, if unattacked. might fully recover. The commonest 

 cases of this kind that we have observed in the islands arc pri- 

 marily due to the interference of man. For instance, such at- 

 tacks commonly follow after a forest fire, trees slightly scorched 

 often becoming badly affected by insects ; forests where previously 

 there has been a dense or uniform growth either of the trees 

 themselves or of the undergrowth, and conse(|uently a great re- 

 tention of moisture, when opened up by cattle or by thinning and 

 so rendered much drier, are very liable to attack, because many 

 of the trees suffer from such change of conditions. That this 

 is true is readily seen from the fact that in virgin forests, never 

 entered by cattle, one never observes this great nudtiplication of 

 individuals of species that attack the timber, and it is possible to 

 search for days in such forests without finding a single individual 

 of such s])ecies. It is a well known fact that the I iawaiian forests 

 are singularly susce])tible to any interference with the natural 

 conditions — in fact, to an extent that is rarely, if ever, seen in 

 the case of forests of other countries. This is i)erfectly natural, 

 when we consider that they have developed under conditions very 



* By Dr. R. C. L. Pprkins. (rrintcd l).v pcrniisHion of the Uiiwaiiiin Su^iir 

 PlnnterH' Experiment Station.) 



