xl FAUNA HAWAIIENSIS 



between 1500 and 2000 ft. elevation, though he has a considerable walk to and 

 from the collecting ground. Almost the last day I collected in that locality, I took 

 exactly that number of beetles (Cis 6 species, Proterhinus 10, Carabidae 5, Curcu- 

 lionidae 7, Histeridae i, Cerambycidae 2, Staphylinidae 1, Nitidulidae 7, Anobiidae i) 

 in addition to numerous other insects, and had it been a different season, stray species 

 of Elateridae would certainly have occurred. I do not doubt I must often have 

 exceeded this number of species, especially as on this occasion 1 was by no means 

 well and really unfit to attempt collecting in the mountains. 



It has been suggested that close interbreeding may result in diminished fertility 

 and in a paucity of individuals of island species, and that such interbreeding is very 

 common there is no doubt. But whether in insects this inbreeding has any such 

 result is extremely doubtful. We can feel quite sure that some of the introduced 

 insects in the islands have originated from one or two, or very few individuals, 

 accidentally imported by man, and of others imported for economic reasons we 

 know this to be the case. Yet though some of the former were introduced at least 

 half a century ago and have produced probably at least several broods a year ever 

 since, and some of the latter complete a generation each month or even more quickly, 

 these all remain as common as ever and show no sign whatever of degeneration or 

 impaired fertility. Of imported insect pests it is sometimes said in a careless manner 

 that these naturally disappear or become insignificant in time from being "played out," 

 but 1 do not doubt that careful investigation will show that in such cases the real 

 cause of decrease is that they become attacked, after a while, by other insects or 

 diseases, and especially by parasites and predators, which transfer their attack by 

 degrees from native species to the foreign immigrant. Deterioration in insects, 

 supposed to be due to inbreeding, is much more probably due to the ill-effects of the 

 unnatural conditions of captivity. The extreme sluggishness of so many of the insects 

 and Mollusca leading to great restriction of locality, which we observe also in the birds, 

 must lead to extreme inbreedino-. We have observed colonies of some of the fliohtless 

 beetles to persist for years in a single tree and where these colonies are isolated from 

 others, no doubt all the inhabitants have resulted from a few stray examples, probably 

 often from one. While the food remains in suitable condition these isolated colonies 

 thrive and become very numerous, but they are, doubtless, often totally exterminated 

 when it becomes no longer suitable, unless, by chance, individuals can reach some other 

 tree fit to supply a breeding ground. Obviously this sluggishness and restriction of 

 range must itself diminish the numbers of individuals of a species, and the tendency 

 of island creatures to limit their range and to specialize their habits is a striking- 

 feature of the fauna. Loss of the powers of ilight is a very common phenomenon 

 in this connection. 



