ON THE GENUS ZETHENIA ; WITH DESCRIPTION 

 OF A NEW SPECIES. 



By Louis B. Prout, F.E.S. 



The eastern Asiatic genus Zethenia (family Geometridse) was 

 established b}^ Motschulsky in a paper on Insects from Japan 

 in Et. Eut. ix. p. 34 (1860), and was well re-characterized by 

 Meyrick (as Zettiema—Y\Q.mQ wrongly written) in Trans. Ent. 

 Soc. Lond. 1892, p. 102 ; so that I need not discuss generic 

 characters, beyond mentioning that I find the normal base of 

 the first subcostal of the fore wing often weak or obsolete, leaving 

 this vein to arise apparently out of the costal, as in the genus 

 Gyadroma, Swinhoe— which, indeed, might perhaps be treated 

 as a subgenus of Zethenia, differing only in secondary sexual 

 structures on the male hind wing. 



The type of the genus is, of course, Z. rufescentaria, Motsch. 

 =co7isociaria, Christ. I do not know on what ground Staudinger 

 queries Motschulsky's older name ; if he means that he cannot 

 determine it at all I would suggest that it is illogical to use the 

 generic name Zethenia for other species than Motschulsky's ; if 

 he merely wishes to indicate a doubt whether the Japanese 

 form is co-specific with that of the mainland (consociaria), he 

 should have catalogued the two provisionally separately, or at 

 least omitted Japan from the given range of the latter ; but I 

 would submit that his excellent figure in vol. x. of 'Iris' sets the 

 identity of the Amur and Japanese forms at rest. 



The second species made known to science was albonotaria, 

 Bremer, described as a Selenia, from East Siberia. Its range 

 is similar to that of rufescentaria, and Bremer (ignorant of 

 Motschulsky's work) treated the last-named as " var. c " of albo- 

 notaria, while Staudinger suggests that the two are perhaps 

 " Darwinian forms." I see no necessity for this, though ad- 

 mittedly the alliance is very close. To me they are full 

 "species," and Mr. A. E. Wileman, who collected for about 

 fourteen years in Japan, and used to beat out both species in 

 abundance, tells me that he never saw any reason to doubt their 

 distinctness. He found rufescentaria the more abundant of the 

 two. I may point out that it is, on the average, the smaller 

 species, has the elbow in the margin of the fore wing (at end 

 of second radial) somewhat less strongly pronounced, usually 

 has the discal spot of hind wing larger and more conspicuous, 

 and the postmedial line of both wings developed (whereas in 

 albonotaria it is expressed by mere series of vein-dots), and never 

 possesses the characteristic mark between third radial and first 

 median, which is never absent in albonotaria, and which gave 

 it its name. Christoph also mentions that the antenna in 

 albonotaria is much more shortly ciliated, and that this 



