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XVII. A7-e Everes arcjiades and coretas distinct sj^ecies? 

 By T. A. Chapman, M.D., F.Z.S. 



[Read May 18, 1908.] 



Plates XIX, XX. 



Me. Tutt asked (Ent. Soc. March IStb, 1908) for further 

 facts bearing on whether coretas was or was not a species 

 distinct frona Everes argiades. Nothwithstanding that 

 Dr. Rebel says they are but one species and that the 

 ancillary appendages of the $ are identical, I thought it 

 desirable to investigate this point for myself, and now 

 report the result as having a most important bearing on 

 the question under consideration, and involving also 

 some interesting principles concerning differentiation of 

 species. 



The facts concerning the ancillary appendages are, 

 without going into descriptive details, that the two forms 

 have different appendages, the differences are very slight 

 but they are very distinct and very constant, so slight that 

 we can quite understand their being overlooked. 



It may be asked, Have such minute differences any 

 value for distinguishing species ? In this particular instance 

 they have. In many species one finds much greater 

 differences in these organs even amongst specimens taken 

 at the same time and place. One finds also greater 

 differences between geographical races which we neverthe- 

 less agree to belong to one species. Why, then, are these 

 minute differences of weight in this instance ? In the first 

 place they are constant as betw^een the two forms ; in the 

 second these two forms in no way suggest that they are 

 geographical races. If we found (say) cirgiades in France, 

 Switzerland and Austria, and coretas in Spain and Italy, 

 one would at once accept the geographical explanation. 

 But the facts are very different ; the two species occur, if 

 not on the same ground, at least within a few miles of each 

 other, from their extreme western distribution at Biarritz 

 or rather Bilbao {argiades occur further west in Asturias, 

 but we know little of their Si^anish distribution) eastwards 

 to Buda-Pesth, and unquestionably could readily cross, so 

 far as geographical difficulties govern the case. 



That the differences between the appendages, slight 



TRANS. ENT. SOC. LOND. 1908. — PART II. (SEPT.) 



