( xcviii ) 



archippus and arthemis were not such as to produce normal 

 fertile offspring was probably to be seen in the fact that all 

 known examples of the hybrid — whether captured or bred — 

 were males. Field's valuable results supported the conclusion 

 that arthemis and astyanax were a single species, but that 

 arthemis and archippus were distinct species. Prof. Poulton 

 suggested that we might understand the origin of astyanax 

 from arthemis by comparison with our own White Admiral, 

 (L. sibylla, L.) and its rare black variety. The intrusion into 

 the south of England of a dark, specially protected butterfly 

 like Pajnlio (Pharmacophagus) philenor, L., would probably 

 cause a gradual increase in the numbers of the Black Admirals, 

 and finally their complete predominance, to the exclusion of 

 the type form, which would still exist further north. Along 

 the zone of overlap we might expect interbreeding with 

 Mendelian results, although the genetic relationship between 

 sibylla and its variety had not as yet, he believed, been deter- 

 mined. Starting from this foundation, gradual changes in 

 the pattern of the " Black Admiral " would probably produce 

 a closer resemblance to the model, just as astyanax has not 

 only lost the conspicuous white markings of arthemis but has 

 also gained a large increase in the greenish or bluish iridescence 

 of the upper surface, and a change in tint, accompanied by a 

 much greater prominence of the reddish markings, on the 

 under surface (Trans. Ent. Soc. Lond., 1908, pp. 471-2). 



It was interesting to observe that arthechippus, so far as 

 one could judge from Field's figures, resembled in two im- 

 portant features the Utah and Arizona species L. (B.) obsoleta, 

 Edwards (hulstii, Edwards), which was itself intermediate in 

 pattern, as well as in the male claspers, between archippus 

 and arthemis, or the closely similar iveidemeyeri, Edwards. 

 One of these features was the distinct representation of the 

 white band of arthemis by a row of white spots crossing the 

 hind- wing; the other was a trace of the linear white mark in 

 area la of the fore-wing, representing the termination of the 

 white fore-wing band upon the inner margin. The former 

 feature was distinct in all four of Field's figures, and strongly 

 marked in those of the captured examples ; the latter was dis- 

 tinct in three figures, two of the bred and one of the captured 



