( 197 ) 



XV. Ohservations upon certdiii species of the Lepi- 

 dopteroHs genus Terias, with descriptions of 

 hitherto niuKoited. forms from Japan. By Arthur 

 G. Butler, F.L.'S., F.Z.S., &c. 



[Read October 0th, Isyi).] 



(Plate VI.) 

 The difficulty of discriminating between the species of 

 the genus Terias has long been admitted by lepidopterists, 

 and many of them have attempted to evade it by 

 regarding the species of this group as extremely liable 

 to variation. 



Now, although it cannot be positively proved that the 

 multitudinous similar forms in this genus are constant 

 to their characters, the examination of a long series of 

 individuals from one locality seems to indicate that 

 hybridization, rather than extreme variation, is the factor 

 which produces the apparent gradations from one type 

 to another. 



In the group of species allied to T. hecahe there are no 

 two more distinct forms than the heavily-bordered type 

 and the species named by M. De L'Orza T. mandarina ; 

 and it is noteworthy that in the first the female is 

 extremely scarce ; in T. mandarina this sex is commoner 

 than the male ; in colouring also the T. liecahe type 

 reminds one of the genus Colias, but T. mandarina is far 

 more like Gonepterij.r ,- yet, with a series of 154 specimens 

 of this section of the genus from Nikko, I have been 

 able to arrange a perfect gradational series of scarcely 

 differing forms from the most heavily-bordered of the 

 Japanese representative of T. hecahe to the palest 

 T. mandarina in which the border has practically dis- 

 appeared. 



Superficially, therefore, it would seem that these 

 apparently very distinct species were wholly untenable, 

 and that the T. anemone of Felder, which stands half- 

 way between their extreme variations, was only one of 

 the gradations which proved them to be identical : this 

 view of the case would commend itself to almost any 

 entomologist who examined merely a selected series of 

 specimens ; but when one carefully compares upwards of 



TRANS. ENT. SOC. 1880. — PART IV. (dEC.) 



