1887.] -lol 



These cases point very strongly to migration as the cause of the abundance of 

 this species ; its occurrence at Torquay being an almost isolated instance of its 

 appearance in Devon. The only inference that can be drawn from these facts, and 

 those already brought before us, is that, after trying to establish itself in this country, 

 it succeeded in holding its own for a few years, but, eventually, found the climate 

 unsuitable, possibly too humid, and, therefore, gradually succumbed. — Gr. T. Baker, 

 16, Clarendon Eoad, Edgbaston : March I6th, 1887. 



7s Aporia cratcegi extinct in England ? — Mr. Tutt, in his notes on this subject 

 fante, -pp. 220, 221), suggests "that migration lies at the bottom of the probable 

 cause of the great falling off observed in the number of this species." By this, I 

 understand Mr. Tutt to mean that the same conditions of the climate of this country, 

 which have been unfavourable to the development and increase of indigenous 

 specimens of this species, and have tended towards its rarity or extinction, have 

 also prevented its recruiting its numbers by migration, or rather immigration, from 

 the Continent. The absence or existence of climatic conditions favourable to im- 

 migration, is, no doubt, the cause of the rarity or abundance, in any year or succession 

 I of years, of Colias Edusa, Colias Hyale, Vanessa cardui, Sphinx convolvuli, and 

 other migratory and cosmopolitan species, but Aporia cratagi cannot, I think, be 

 placed in the same category as these, and before we can entertain the hope that it 

 "will become common again" when "we get a fresh stock from the Continent," it is 

 necessary that some evidence should be forthcoming that it is migratory in its habits. 

 According to my experience, Aporia cratagi, although a powerful flyer, and capable 

 of soaring to a great height when pursued or alarmed, is usually a gregarious and 

 sluggish insect, occurring chiefly in colonies, in the immediate neighbourhood of the 

 trees or shrubs on which it fed in its larval stage, and in this respect resembling 

 species of the genus Melitaa. If A. cratagi is migratory in its habits, why do we 

 not occasionally hear of its capture in Kent, and other parts of the South East of 

 England, in those seasons when a larger number than usual of such species as Pieris 

 Daplidice, Argynnis Lathonia, and other immigrants from the Continent occur .-' 

 As it is an abundant species in many parts of the Continent of Europe there ought 

 not to be any difliculty in ascertaining from Continental Lepidopterists whether or 

 not it is migratory iu its habits. 



With reference to the concluding remarks of Mr. Tutt, I fail to see how the 

 prejudice to Continental types of British species, which may possibly still be enter- 

 tained by some collectors of British Lepidoptera, can affect the consideration of 

 questions concerning the geographical distribution or migration of species. — H. Goss, 

 Surbiton Hill : March, 1887. 



[We shall be glad of precise information on the point raised by Mr. Goss. At 

 present we are disposed to agree with him to the effect that A. cratagi is not a 

 migi-atory species, and think that any hope of resuscitating it in this country must 

 rest on artificial introduction and perfect abstention from "collecting" for a long 

 time. Not believing, as a rule, in extermination by collectors, we are, nevertheless, 

 disposed to think that " over-collecting " may have played a prominent part in the 

 disappearance of this butterfly, viewed in connection with its gregarious habits in its 

 earlier stages (which rendered it an easy prey to wholesale collectors) and its 

 " localization " here. But we are compelled to adopt the idea that the decadence of 



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