INTRODUCTION li 



sometimes seen on the wing. Some may overlap with the flightless forms in their 

 habitat, but on the whole the two groups are quite distinct. The apterous 

 Emesiidae are also terrestrial. The Elaterid, Dacnitus, is terrestrial, as is the Lucanid, 

 Apterocyclus. Many of the flightless insects are conspicuous for their sluggishness, 

 e.g. the subapterous Nitidulidae, and amongst these we find the only terrestrial species 

 of this family. Many of the Carabidae that are flightless are arboreal in their 

 habits, but these are all able to run quickly, and many of them are extraordinarily 

 active. It must be remembered that in creatures inhabiting a dense forest belt, as 

 most Hawaiian insects do, many of these, when in search of new feeding grounds, 

 at most require to descend from one tree and ascend another. Predaceous creatures 

 like Carabidae and many of the feeders on dead wood, as we have often observed, 

 infest the same tree year after year, and probably only cease to do so as the tree 

 itself fails to afford suitable food for the creatures that it supports, both those 

 that feed on its substance and those which prey on these. Doubtless with very 

 sluggish, flightless beetles the death of a tree often entails the death of numerous 

 individuals, but during its occupation by generation after generation, individuals may 

 become dispersed and colonize adjoining trees. In the case of more active forms 

 like the Carabidae, the death of a tree, that is their home, need cause no loss of life 

 of the beetles. It is instructive to note that in the case of beetles, which require 

 for their food that a tree should be in a special state of disease or decay, lasting only 

 for a short period, e.g. the bark-eating Longicorn beetles, and the burrowing Scolytidae, 

 no case of loss of flight is known to occur. That many creatures, which find an 

 inexhaustible food supply within a very small area, should become more and more 

 sluggish or loth to fly, and finally by disuse lose their powers of flight, seems quite 

 natural. Natural selection may have prevented the loss of flight organs in some of 

 the island creatures, but it has probably had nothing to do with the degeneration of 

 the wings in the flightless ones. Had any of the Plagithmysine Longicorns or the 

 Passerine birds taken to a terrestrial life, we should probably find flightless examples 

 of these, as we do in the Nitidulid beetles and in the (now extinct) small rails of the 

 genus Pennu/a. On the other hand sluggish Nitidulid beetles that affect flowers are 

 never flightless for obvious reasons. 



Except in one or two isolated and doubtful cases {Cis and Bembidmm) there 

 are no instances known in the endemic Coleoptera or Heteropterous bugs, where a 

 species has both fully-winged and flightless individuals. In fact the only case known 

 where, apart from the condition of the wings, individual beetles are apparently in- 

 separable, is that of Bembidium fnolokaiense (winged) and Nesocidium laeticulum 

 (flightless). In the Homopterous bugs, however, we have fully-winged and flightless 

 forms of some species, e.g. of Aloha ipomoeae and Nesosydne ipomoeicola, of which 

 fully-winged forms are only produced at times and are then less numerous than the 

 brachypterous. These species both occur outside the forest. Of those found only in 



