HI FAUNA HAWAIIENSIS 



the forest on ferns or trees I know no such cases of dimorphism, so, if any exist, they 

 must be rare. Many species are only known as fully-winged forms, e.g. the several 

 species of Aloha that feed on the Myrtaceous tree Metrosiderus. Most of the species 

 of the extensive genus Nesosydne are flightless, but A^. koae appears to be always 

 fully winged. This latter, though it feeds on a common and gregarious tree {Acacia 

 koa), yet appears to have peculiar habits, so that few Koa trees, as a rule, are in a 

 condition to support it, since they bear no true leaves. Whether this fact concerns 

 the retention of the organs of flight is worthy of investigation. In fact a careful 

 study of the winged and wingless forest-frequenting species of Nesosydne would be 

 of considerable interest. 



Probable origin of the existing fauna from very few immigrants, the large 

 genera, or group of allied genera originating from a single or few ancient 

 immigrants. Comparison with the Flora. 



When we look at the Hawaiian fauna as a whole we cannot help remarking the 

 numerous genera, which comprise an inordinate number of species. Also, we note 

 that a tribe or subdivision of a family will be represented by a number of closely allied 

 genera, these together including many species. Or, as in the Drepanidid birds, a family 

 may contain many closely allied genera, though these have but few species. A few 

 characteristic examples may be cited. In insects, of the Lepidoptera, Scotorythra 

 (Selidosemidae) has more than thirty species ; Scoparia (Pyraustidae) about 60 ; 

 Thyrcopa (Gelechiidae) about 30 ; Aphtlionetus and Neelysia (Hyponomeutidae) each 

 about as many as the preceding, and Hyposmochonia of the same family about 1 80 ; 

 Heterocrossa (Carposinidae) contains more than 30 species. Of many of these, species 

 still undescribed are also known. In Coleoptera, Oodeiiias (Cossonidae) has 46 species; 

 Proterhinus (Proterhinidae) no less than 136; while the Cerambycid genus Plagitk- 

 mysiis has 2)2) ; Xyletobius and Mirostermis (Anobiidae) have 52 and 70 species. In 

 the Odonata or dragonflies, Agrioii has two dozen species, and the Neuropterous 

 Anomalochrysa (Hemerobiidae) thirty. The genera Nysuis and Reduviolus in Hemi- 

 ptera, together with about 50 species, form nearly 40 per cent, of the endemic 

 Heteroptera, while the Homopterous Nesophrosyne has a multitude of forms, 42 having 

 been described. In Hymenoptera, Odyneriis (Eumenidae) has nearly 100 species, and 

 Nesoprosopis (Prosopidae) more than 50. 



The Molluscan genus Achatinella contains 107 species, as enumerated by Sykes, 

 Amash'a loi, and Leptachatina 75. Even allowing that many of the described species 

 may prove to be only varieties of others, the genera are of very large extent. 



With regard to series of genera that are closely allied to one another, it will be 

 noticed that many of the genera already named as containing a great number of species, 

 have themselves given rise to offshoots of generic value, i.e. have produced species 



