INTRODUCTION xli 



Number of species of insects and causes of extinction. 



The total number of Hawaiian insects known to me at the present time is about 

 3325, but of these only about 2740 can be considered as belonging to the natural 

 fauna. Owing to man's interference and his introduction of foreign creatures, I should 

 consider that about 300 species have been exterminated, without being collected. 

 Mr Blackburn's and my own collecting, together with some aid received from others, 

 has in my opinion resulted in the collection of about half of the e.xisting species of 

 native insects, so that a perfect collection of this section of the fauna, made before 

 man's interference, might have yielded about 5780 species. I may have somewhat 

 underestimated the number exterminated. 



It is known that several species of Passerine birds, formerly abundant, had become 

 either totally or nearly extinct before I came to the islands, twenty years ago, and 

 there is reason to fear that several others may since have disappeared. At any rate, 

 we know certainly that some, which were abundant, have become much less so, and 

 have totally disappeared from localities where they were common enough. In my 

 paper on the birds (Vol. i, p. 393) I have referred to the causes which have brought 

 about this extinction or diminution in numbers. As with the birds, destruction of forest 

 has, doubtless, caused the disappearance of many local insects, but even of greater 

 importance has been the introduction of foreign carnivorous species, especially of the 

 dominant ant, Pheidole megacephala. There is no record of the time when this destruc- 

 tive creature was imported, but even during the last twenty years it has occupied some 

 considerable areas previously free from it. It may be said that no native Hawaiian 

 Coleopterous insect can resist this predator, and it is practically useless to attempt 

 to collect where it is well established. Just on the limits of its range one may 

 occasionally meet with a few active beetles, e.g. species of Plagithmysus, often with 

 these ants attached to their legs or bodies, but sooner or later they are quite ex- 

 terminated from such localities. It is quite certain that native beetles and many other 

 insects are absent from the localities occupied by Pheidole, solely on account of its 

 presence. In several instances, as the ant has been observed to occupy a new area, 

 this area having been collected over before it was present and yielding many native 

 beetles, the latter have entirely disappeared. In a few low-lying localities, even close 

 to the coast, there are some places, which from excessive dryness and other causes, 

 the Pheidole is unable to occupy, at any rate permanently, and yet unfavourable, 

 as these are, for insects of any kind, here only will native Coleoptera be found. 

 On one occasion I came across an instructive instance of the effect of these ants 

 on the native fauna. A more or less open piece of forest at an elevation of 1500 ft. 

 above sea-level, with a large variety of trees scattered in it, appeared at first sight 

 an excellent spot for collecting native insects. A number of native Hymenoptera 

 F. H. I. / 



