132 FAUNA HAWAIIENSIS 



Arrangement of Genera in order of time. 



From a consideration of the foregoing analysis we can now with considerable 

 probability group the genera under successive periods of time, and indicate the nature 

 of the geographical influences of each period, beginning with the most ancient. 



First Period. 



To this belong 7 genera, viz. Sisyrophyta, Scotorythra (Selidosemidae), and 

 Scoparia, Promylaea, Mestolobes, Orthomecyna, Protaulacistis (Pyraustidae), with 133 

 species. Probably all these must be traced to a South Pacific origin, and the former 

 existence of a considerable land-area (now submerged) between New Zealand and 

 South America is postulated. 



Second Period. 



Here are referred 5 genera, viz. Agrotis (except 2 species), Eucymatoge, Omiodes, 

 Pyrausta, and Phlyciaenia, with 80 species. Of these the first only is American in 

 origin, the other four Asiatic. Possibly this period may coincide in time with the 

 considerable extension of the Hawaiian Islands to the north-west which seems to have 

 once existed. 



Third Period. 



This includes 18 genera and 48 species. Of the genera 6 are probably Australian 

 or New Zealand in origin [Dasytiris, Progonostola, Xanthorhoe, Homoeosoma, Geno- 

 phantis, Talis), 5 Asiatic {Hypenodes, Cosmophila, Hydrioniena, Lycaena, Margaronid), 

 and 5 North American {Nesamiptis, Vanessa (i species), Prionopteryx, Mecyna, 

 Loxostege), showing a nearly balanced equality of influence which implies circumstances 

 much as at present. Leucania and Deilephila (4 species) are of doubtful import. 



Fourth Period. 



This is represented by 29 species, contained in 21 genera, viz. Agrotis (2 species), 

 Deilephila (i species), Vanessa (3 species), Lycaena (i species), and the 17 genera 

 recited above as wholly apodemic. Excluding 9 of these genera, which are presumably 

 of artificial introduction, and 7 other species which are practically cosmopolitan, there 

 remain only 1 1 species, of which 5 are certainly and 2 probably of American origin, 

 and 4 presumably Asiatic. The preponderance of the American element (I think a 

 majority of the cosmopolitan species probably also came from that side) seems to 

 be explained by the fact that almost all these species possess great powers of flight, 

 and find little obstacle in mere distance, but are by no means independent of the wind ; 

 this effect is therefore traceable to the influence of the N.E. Trade-winds. 



