A R C A S imperialis. 

 Emerald Hair-streak. 



Tribe, Papiliones. Family, Polyommatidae. Sub-I'aniily, Tliedanae. 



Kob. 



Sub-Generic Character. 



Pal])i, ill both sexes, very long, thick, porrect, twice as long as the 

 head, curved downwards, all the joints entirely covered with 

 close-set scales, posterior wings six-tailed. 



Specific Character. 



Above shining blue: beneath emerald-green, marked uilh minute 

 black waved lines. 



Papilio imperialis. Cramer, PI. 75. /. E. F. 



Hesperia Venus. Fab. Ent. Sys. 3. 1 . 268, 



It is impossible to depicture with correctness, the resplen- 

 dant blue which ornaments the upper surface, or the vivid 

 emerald green on the under wings, of this rare and splendid 

 insect. It is possessed by few collectors ; nor did we cap- 

 ture more than three specimens, during two years devoted 

 to the entomology and ornithology of Brazil. The male is 

 distinguished by a black central spot on the anterior wings. 

 The very remarkable prolongation of the palpi, which arc 

 alike in iDOth sexes, induces us to consider this insect as a 

 type of form, or in other words, a sub-genus : but we are at 

 present unprepared to state any thing satisfactory on its 

 true affinities. 



We have thought it right in this and other instances, 

 to retain the original specific name of Cramer ; and we 

 shall do the same in all instances where it Avill not ])ro- 

 duce a discordant union of generic and specific names. On 

 this head, as the principle of Linnicus, from the great 

 number of new genera since defined, can no longer be acted 

 upon, we think that specific appellations, derived from 

 some character of the insect, are much better, in every 

 respect, than attempting to render the nomenclature of the 

 Lepidoptera a correct index to the mythology of the 

 Ancients. 



88. 



