122 



BRITISH BUTTERFLIES. 



which seemed to combine Hie characters of the 

 other two, and its geographical position, the 

 county of Durham, was intermediate between 

 them. Until the publication of this third 

 species, or supposed species, no doubt appears 

 to have been expressed of the distinctness of 

 the other two. But when a new species of 

 insect is discovered, which in its general 

 characters is intermediate between two old 

 ones in colouration, ornamonta'ion, and geo- 

 graphical position, an opinion perhaps I 

 should say, a suspicion will ar sc that the in- 

 termediate species connects the other two, and 

 that the three constitute but a single species. 

 I scarcely know whether such an opinion was 

 immediately made public, but still the ques- 

 tion appears to have been discussed, since 

 Mr. Wailes, a gentleman of profound obser- 

 vation and research, believed it incumbent on 

 him to defend the newly-propos"d species, 

 which he did at page 42 of the first volume 

 of the " Entomological Magazine," in these 

 words : Polyommatus Salmacis I entirely 

 coincide with Mr. Stephens in considering 

 this a distinct species." This opinion, or 

 rather decision, was received with great 

 deference, and was justly regarded as one of 

 importance, since it must be evident that the 

 existence of a distinct species intermediate 

 between two other species was an a priori 

 argument in favour of the perfect distinctness 

 of those other species. Mr. Dale was, I 

 believe, the first entomologist who expressed 

 a decided opinion adverse to the claims of 

 Salmacis as a distinct species. At page 357 of 

 the first volume of the " Entomological Maga- 

 zine," Mr. Dale writes thus : " P. Salmacis, 

 or Titus, is intermediate between Agestis and 

 Artaxerxes ; in Scotland none of the Agestis 

 are to be found, they are all Artaxerxes ; in 

 the south none of the Artaxerxes are to be 

 found, they are all Agestis. At Newcastle 

 they appear to be mules, or hybrids between 

 the two species, partaking in some degree of 

 the characters of both ; some of the varieties 

 have a black spot inside the white one on the 

 upper surface of the first wings." This was 

 published in 1832 ; and in the January of 

 1834, after having devoted much time and 



attention to Mr. Dale's opinion, as expressed 

 above, I publi-hed an opinion of my own, 

 which went perhaps rather further than Mr. 

 Dale's in the same direction. I stated, that 

 'having examined specimens of Polyommatua 

 Agestis from different localities, I have arrived 

 at a conclusion which 'will not, I fear, be 

 coincided in by many of our lepidopterists. 

 On the south downs of Sussex and Kent Agestis 

 assumes what may be called its typical form. 

 I have taken it at Ramsgate, Dover, Hythe, 

 Hastings, Rye, Brighton, Worthing, Little- 

 hampton, Chichester, and Portsmouth; in the 

 Isle of Wight, in Dorsetshire, and in Somer- 

 setshire ; and throughout tlds range it is very 

 similar : then, going northwards, I have met 

 with it at Worcester, LeominsterjBirmingham, 

 and Shrewsbury and here an evident change 

 has taken place : theband of rust coloured spots 

 has become less bright : at Manchester these 

 spots have left the upper wing almost entirely : 

 at Castle Eden Dene they are scarcely to be 

 traced, and a black spot in the centre of the 

 upper wing becomes fringed with white ; in 

 some specimens it is quite white, as shown at 

 page 126 : it then changes its name toSalmacis. 

 We proceed farther northwards, and the black 

 pupil leaves the eyes on the under side, until 

 at Edinburgh they are quite gone , then it is 

 called Artaxerxes. The conclusion I arrive at 

 is this: that Medon, Salmacis, and Artaxerxes 

 are nothing more than geographical races of 

 one species." Mr. Wailes, in his admirable 

 " Catalogue of the LepMoptera of Northumber- 

 land and Durham," seems to think this con- 

 clusion erroneous, for he says "Mr. Newman, 

 in the second volume of the ' Entomological 



O 



Magazine,' advanced an opinion that all three 

 were one, though 1 certainly think on insuffi- 

 cient grounds." P. 217. Mr. Wailes then 

 goes very carefully over the ground, and after 

 five pages of lucid and e'aborate reasoning, he 

 arrives at the following conclusion : "From 

 all these facts and circumstances I think I am 

 justified in uniting the three forms under the 

 single name of Medon.' 1 P. 223. Thus Mr. 

 Wailes seems to retract his original opinion, 

 and to arrive at the same terminus as myself, 

 by a line of his own construction an issue 



