INTRODUCTION xlv 



immigration would probably take place in ages, if at all. At any period of the history 

 of the islands these chance immigrants must be very few in number, for reasons stated 

 elsewhere, and owing to the obscure nature of the fauna (obscure insects being very 

 imperfectly known in other tropical countries) we cannot be sure whether certain species 

 suspected of being immigrants are really so, as they have not been detected elsewhere, 

 and they may in reality be endemic. This is unfortunate, because they are the potential 

 ancestors of future endemic forms. Thus the Cossonid beetles Deinocossonus and 

 Orothreptes are possible immigrants and so are such species as Prays fulvocanel/us in 

 Lepidoptera, but they have not been recorded from other countries. A very few 

 species, e.g. the Tortricid moth, Bactra stramznea, are almost certainly immigrant. If 

 we examine these supposedly immigrant species and in conjunction with these consider 

 those endemic ones, which are little modified from outside forms, and therefore are to 

 be considered as a development from the more recent immigrants, we find a very 

 different condition from that above noted in the case of introduced species. There 

 may be a few constant species amongst these, and this may be due to the fact that such 

 have been comparatively a short time in the islands and are the most recent natural 

 immigrants, but these are certainly very few. We at once note the large amount of 

 variability exhibited by the species. In this connection we may review a few species, 

 which are either the sole representatives of their genus (and not, or very little, different 

 from the outside forms) or at least have only one or two other species related to them 

 in the islands. In the Aculeate Hymenoptera, the small ant Ponera perkinsi, hardly 

 separable from foreign species is the sole native representative of its group. It is 

 widely spread, occurs in many localities from near the coast to above 4000 ft., and 

 exhibits considerable variation. There is sometimes a distinct tendency to specializa- 

 tion in variation in different localities. In the parasitic Hymenoptera, Echthroinoiplia 

 inaculipennis varies very greatly and individuals might at first be taken to represent 

 distinct species. The small cockroach Phyllodromia obtusata is notably variable, so as 

 almost to have given rise to a distinct species in parts of the island of Molokai. The 

 earwigs listed under the names of Anisolabis pacifica and inaritinta in the systematic 

 portion of this work, the former possibly endemic and the latter immigrant, are variable. 

 The forest-frequenting species of Caloternies, which I expect will prove to be peculiar 

 to the islands, exhibits notable variation in different localities. Bactra straininea, a 

 New Zealand moth, is excessively variable and I consider that some of its local forms 

 will probably prove to be distinct species. Another small moth Hypenodes altivolans, 

 some varieties of which differ very little from the widespread H. costaestrigalis, is 

 extraordinarily variable. The Pentatomid bug Oechalia grisea varies very greatly, and 

 there is at least one offshoot of this, of restricted habitat and forming a distinct species. 

 In birds the native duck, possibly a puny descendant ol Anas boschas, is so variable 

 that some ornithologists have supposed we have more than one species. In beetles 

 Pentarthrum prolixuvi and the Parandra are variable forms. It is of course possible 



