ii8 FAUNA HAWAIIENSIS 



The discrimination of species in this group is a matter of some Uttle difficulty. We 

 have a fair knowledge of the European species, but only a fragmentary and inadequate 

 acquaintance with extra-European forms. The characters relied on by European 

 authorities are the shape and size of the setigerous granules on the tegmina, the form 

 of the vertex and the colouring of various parts : the first and last I have found of little 

 or no value ', the second of some degree of worth, but even in this there is some little 

 amount of variation — to how great an extent caused by shrinking in dried specimens I 

 am not sure. In what appears to be the same species the frons and clypeus may be black 

 or pallid or varying between the two. There is, however, usually a more or less large 

 pallid spot at the sides near the junction of these two parts ; the pronotum may be 

 black entirely, or pallid entirely, or black with more or less widely pallid margins. The 

 scutellum may be entirely black, or entirely pallid, or black with ferruginous or pallid 

 keels'. In lolaiiia the ^ genital segments are comparatively simple, but are very 

 complex in Oliarus, and I have not used them for specific purposes at present, until 

 1 have had an opportunity of examining American or Polynesian material. 



In these two genera the frons and vertex are contiguous, but separated by a 

 portion of the head which appears truncate when the head is viewed in profile. This 

 I have called the "fossette." It is keeled on each side and is more or less hollowed 

 out. It is usually simple, or more or less obscurely (generally very obscurely) carinate 

 medio-longitudinally ; in Oliariis taviehanieha and orono, however, it is distinctly 

 longitudinally bicarinate. Fieber and Melichar consider this part of the head as a 

 portion of the vertex, while some authors apparently treat it as part of the frons. 



The genera are easily recognized as follows : 



Scutellum with 3 keels; costal margin, of tegmina strongly granulate {i) lolania Kirk. 



Scutellum with 5 keels; costal margin not or only obscurely granulate {2) Olinnis^'iW. 



IoL.\Ni.\, gen. nov. 



Allied to Cixius Latreille, but differing principally by the structure of the vertex. 



Vertex anteriorly considerably narrowed, apical margin acutangularly produced 

 beyond apical margin of eyes, base of vertex deeply roundl)- emarginate ; vertex 

 hollowed out, not (or very obscurely) medio-longitudinally carinate. Middle carina 

 of the evanescent posteriorly. Front as in Cixius, two ocelli (or a third, very obscure). 

 Posterior tibiae with very feeble spinelets. Type I. perkinsi Kirk. 



' In Hawaiian forms. 



" In the palaearctic forms, species are based upon the colour — (i) black or (2) ferruginous — of the 

 scutellar keels. Is not the ferruginous colour, and still more the pallid colour in some Hawaiian forms, due 

 simjjl)' to arrested ontogenetic colour-development ? 



