Ivi FAUNA HAWAIIENSIS 



It must be confessed that the extreme forms of Hawaiian Anchomenini are very 

 unlilce one another, yet no single genus (as in the case of the birds of the family 

 Drepanididae) appears to be very isolated from its nearest ally. Probably each is more 

 nearly related to its neighbour than to any outside form, and this seems to me in favour 

 of the whole series having been evolved from a single form, anciently immigrant. 

 In any case the possibility of the series having originated from numerous Anchomenine 

 immigrants at various periods of time, each of these immigrants having been such as 

 to fit naturally into the existing series, or at least having given origin to forms that do 

 so fit in, seems very improbable. Should one even propose two ancestral immigrant 

 forms, one most like Colpocacctis or Mysticomenus (central in the existing series), a 

 fully-winged insect giving rise to the series of genera with simple tarsi, and now mostly 

 flightless, the other perhaps flightless and akin to Platynus, giving origin to the series 

 with grooved tarsi and at the same time all flightless, the great resemblance between 

 Colpocaccns and Mysticomenus, the one with grooved, the other with simple tarsi, and 

 the specific differences in the development of the grooves of the former, may cause him 

 to hesitate to admit even a dual origin for the whole series. 



The case of the Hawaiian Pterostichini is much simpler than that of the Ancho- 

 menini. There are only four genera, intimately allied, and separated solely by the 

 characters of the pronotal setae. Several of the species are now known to be almost 

 certainly inconstant in these characters, since individuals, not otherwise different, have 

 been found in company (in a ' batch ') both with and without certain of these setae. 

 Consequently individuals of one species fall into two genera on the pronotal chaetotaxy. 

 As in the Anchomenini, there is a great diversity of appearance in the members of this 

 group, and here again the setal characters appear to sunder species that are really 

 allied. The large series of existing species do not seem to have required more than 

 a single immigrant species for their evolution. The less diversity of structure as 

 compared with the Anchomenini, I judge to be due merely to the fact that sufficient 

 time has not elapsed for its production. Whereas the Anchomenine Carabidae are now 

 spread over all the islands, the Pterostichines, whose head-quarters are clearly on the 

 central islands (Maui and Molokai) where probably they first became established, are 

 at present not known at all on Kauai (admirably adapted as is that island for their 

 occupation), and even on Oahu are sparsely represented by a few more or less common- 

 place forms. Looking at the most remarkable of the existing Pterostichines in the 

 islands, it does not require a great stretch of the imagination to see in these the 

 progenitors of future genera as distinct from the more commonplace forms, as are the 

 more remarkable Anchomenini, the genus Blackbui-nia, for example, from the more 

 commonplace Anchomenines. The Hawaiian Pterostichines, speaking generally, are in 

 a wide sense hardly more than flightless forms of Cyclotliorax, a genus of a few species 

 in the Australian region, a fact in itself opposed to the probability of their having arisen 

 from various immigrant species. 



A comparative study of many groups of animals represented in the islands, and of the 



