198 



Dr. Perkins, in liis Introduction to tlie Fanna Hawaii- 

 ensis, has surveyed the insect fanna of the Archipelago in a 

 masterly manner, and tonched npon some of the fundamental 

 problems connected ^ith its origin and evolution. It remains 

 for Hawaiian entomologists to periodically survey each family 

 in the light of increased knowledge, see how far the new facts 

 support old theories, or what new theories they lend their aid 

 to, and to indicate in what direction more details should he 

 accumulated. The following is an attempt at such a survey of 

 the species dealt with in the first part of this paper. 



The family of Delphacidae, as represented in the Archi- 

 pelago, exhibits the same phenomena as are observed -in most 

 of the families represented in the native fauna. In it one finds 

 a few foreign species, some of which are introductions since 

 the advent of the white man ; a certain numl)er of native spe- 

 cies of foreign genera, which may eventually be discovered 

 elsewhere ; and a large number of species forming closely re- 

 lated autochthonous genera, the species themselves being often 

 polymorphic groups of individuals forming races, varieties or 

 subspecies, which in many cases show distinct geographical or 

 topographical grouping, as do many of the recognized species. 



All these phenomena are well exhibited in the family under 

 re^'iew. In PerkinsieUa saccharlcida and Peregrinus maidis 

 we have two foreign species introduced into the Islands in 

 quite recent times, both of economic importance, and the for- 

 mer, on account of the work done in its control by introduced 

 parasites, of great biological interest. Three species of Kelwia 

 (sporobolicola, pallidum and sivezeyi) represent the native spe- 

 cies of foreign genera, all living in the lowlands on grasses 

 and sedges, a habitat and food not used by the species of the 

 autochthonous genera ; these may eventually be 'found to be 

 foreign species. It is the species forming the autochthonous 

 genera that present the greatest interest and with which this 

 Review deals. 



Hawaii Oceaxic or Contixextal? 



Before considering the origin of the Hawaiian fauna it is 

 first necessary to come to a decision as to the character of the 

 Archipelago. Is it a purely oceanic area with a fauna (and 

 flora) descended from a limited number of inmiigTants, Avho 

 arrived by natural means of dispersal over large ocean areas, 



