102 tSe entomologist. 



environment would be more severe, but that they are now 

 retained not because they are any longer required for the same 

 purpose, but by reason that they prove of value in other ways ; 

 thus, in the case of ocellation in the genus Erchia, for purposes 

 of specific identity and recognition ; and, in the case of melanism, 

 as enabling its male possessors to compete more successfully 

 for the members of the other sex, by reason of their enhanced 

 vitality. 



Birmingham, Dec. 14th, 1898. 



THE PROBABLE CAUSES OF THE DECADENCE 

 OF BRITISH RHOPALOCERA. 



By G. Harold Conquest. 



With reference to Mr. W. Harcourt-Bath's interesting article 

 on this subject {ante, p. 55), I should like to state that it appears 

 to me that Mr. Bath does not lay nearly sufficient stress upon the 

 operations of agriculture as a factor in the extinction in so many 

 localities of the rarer of our British Rhopalocera. 



I should say ninety-five per cent, of the extinction has been 

 caused by the operations of our friend the farmer, i. e. in the 

 cutting down of our woods and forests, the draining of our fens 

 and marshes, the burning of the furze and indigenous flora of 

 our hillsides, and all the various operations incident to the 

 improvement of the land from a farmer's point of view. 



It seems almost puerile to hold collectors, law of amixia, bad 

 seasons, &c., responsible, when one considers the vast changes 

 that agriculture has wrought over the face of a great portion of 

 the British Islands daring even the last hundred years, and the 

 enormous destruction of large classes of lepidopterous insects, 

 including of course the Rhopalocera, consequent thereon. 



The following examples will, I think, support my contention 

 that it is to the operations of agriculture that the extinction or 

 rarity of many of our British butterflies is chiefly due : — 



Papilio machaon. — Formerly abundant in the fen-lands of 

 Cambridgeshire and Huntingdonshire ; now, owing entirely to 

 the drainage of the fens for agricultural purposes, confined to 

 the small area of Wicken Feu in Cambridgeshire. P. machaon 

 is of course still plentiful in the Norfolk broad district, owing to 

 the fact that its habitat there has not been destroyed for agri- 

 cultural purposes. 



Polyuininatus dispar. — Exiinci as a British insect, owing to 

 the destruction of its habitat for agricultural purposes. 



Apatura ^ iris, Liinenitis sibylla. — Formerly in comparative 

 abundance in many localities ; now comparatively rare, and 



