INTRODUCTION liii 



judged to be more different from the aggregate of species they contain, than are these 

 one from another. In the Carabidae, tlie Anchomenini contain 17 genera more or less 

 closely allied to one another, and the Pterostichini four, the latter tribe with 76 species, 

 the former with 106. The Plagithmysini of the Cerambycidae contain three closely 

 allied genera, and the Prognathogrylline crickets (Gryllidae) four. 



It becomes of importance to consider whether these great series of congeneric 

 species and smaller series of allied genera have been developed in the islands from 

 a single anciently immigrant ancestor in each case, or have sprung from diverse ancient 

 immigrations. Are we to consider that Drepanid birds, Anchomenine beetles, moths 

 of the genus Hyposmochoina and Scotorythra, etc. etc., have more or less frequently 

 safely reached the islands in past times and become established ? If this be the case 

 the successful immigration of outside animals must have been of comparatively common 

 occurrence. If we are able to say in any instance that in the case of one of these 

 series, whether of genera or species, that one species or genus is more closely allied 

 to some foreign form while another is more closely allied to a second foreign form, 

 than are the Hawaiian species or genera to one another, we should naturally suppose 

 these to be of different origin. Thus the moths of the genus Margaronia are very 

 different, and clearly belong to quite different groups existing outside the islands, and 

 cannot be supposed to have developed within these from a common immigrant ancestor. 

 One in fact {J/, exaula) differs very slightly from foreign species, and the fact that its 

 caterpillars are sometimes found feeding on imported shrubs growing in gardens in 

 Honolulu renders the endemicity of the species very doubtful. It is probably an 

 importation by man and will be found elsewhere. 



In a few cases, however, we can, from a study of the structures of the truly native 

 insects and a comparison with outside forms, be sure that the existing species are not 

 sprung from a single ancient immigrant species. This is the case with the great series 

 of Hawaiian wasps of the genus Odyneriis, one group of which [O. nigripennis and 

 its allies) is closely related to Oriental species, and entirely different from the other 

 members of the genus. I suspect that the endemic moths of the genus Agrotis are 

 similarly of diverse origin. If we consider the habits and distribution of these genera, 

 that both are dominant forms, almost cosmopolitan, that in almost every country species 

 of each of them are excessively numerous in individuals, we shall not be surprised that 

 individuals of more than one species of each have at different times reached the islands. 

 Moreover, it should be said that neither Odynerus nor Agrotis (s.l.) are the equivalents 

 of ordinary genera, but comprise a heterogeneous mass of forms, which either remain 

 unclassified or at least are imperfectly understood as to their relationships. 



Many of the genera that contain a very long series of endemic species are them- 

 selves peculiar to the islands, many in fact are so highly endemic that their relationship 

 to outside forms is by no means close, or even so remote as to be involved in doubt. 

 The time that has been necessary for the isolation of such remarkable genera may well 



