I JO FAUNA HAWAIIENSIS 



SCOTORYTHRA Butl. 



Face with tuft of scales. Tongue developed. Antennae in t bipectinated, simple 

 towards base (on 4 or 5 joints above basal) and on apical third. Palpi rough-scaled. 

 Thorax hairy beneath. Femora sometimes hairy beneath, posterior tibiae in ^ more or 

 less dilated, containing hair-pencil in groove, posterior tarsi in ^ often reduced. Fore- 

 wings in Z without fovea; 10 often connected with 9, 11 rarel)' out of 10 very near 

 base, rarely absent, sometimes anastomosing with 12. Hindwings normal. 



Type ^. arboricolans Butl. This genus is endemic ; the species are exceedingly 

 puzzling, owing to their number, similarity, and similar variability. In the males the 

 secondary sexual characters, such as the length of the abdomen (measured in terms of 

 the breadth of the hindwings), the length of the antennal pectinations (estimated in 

 terms of the breadth of the stalk), and the structure of the posterior legs (the tarsi 

 being measured in terms of the length of the tibia), often afford valuable aid in their 

 discrimination ; but the females of allied species are often excessively similar. 



In the neuration of the forewings, the origin of i i out of 10 very near base, or its 

 entire absence, appear to be individual abnormalities, which I have observed only in 

 one instance of each, of no specific importance ; the connection of 10 with 9 is frequent, 

 but (as in Selidosema and allied genera) is also of no importance ; the anastomosing of 

 1 1 with I 2 however is worthy of attention, as 1 have found it in some specimens of all 

 the first eight species (except corticea, not examined), even in the three monotypic ones, 

 it being most constant in isospora, whilst I have noticed no instance of it in the rest ; it 

 therefore helps to confirm the grouping of these species together, though too inconstant 

 to define them ; these eight species are however distinguished from all the rest by the 

 form of the second line. 



In the following tabulation the scheme is double from the eighteenth heading 

 onwards, the sexes being thereafter tabulated separately ; this was unavoidable, owing 

 to the divergence of the sexes in these species ; the discrimination of the males is then 

 rendered comparatively easy by the use of the secondary sexual characters ; that of the 

 females is and must remain difficult, the differences between them being extremely 

 slight, and the individual variability very considerable. 



1. Apex of forewings subfalcate ; expanse over 80 mm. ( ? only known) (jo) megalophylla. 



„ „ at most somewhat prominent ; expanse under 76 mm 2. 



2. Postmedian line of hindwings well-defined, slender, entire 3. 



„ ,, dotted or cloudy or obsolete 5. 



3. Forewings ochreous (14) demetrias. 



,, not ochreous 4. 



4. First line of forewings acutely angulated above middle {ij) oxyphractis. 



„ „ almost straight (^16) ortharcha. 



