THE YOUNG NATURALIST. 



179 



ARE BUTTERFLIES DISAPPEARING FROM 

 THE BRITISH ISLES ? 



By JOHN E. ROBSON. 



Further communications on this subject have come to hand, but as they 

 contain little or nothing that has not been said by others it seems needless to 

 allow the discussion to drag on till it becomes wearisome, and I therefore 

 give my promised summing up. 



All correspondents have agreed with the general conclusion at which I had 

 arrived, though they differ more or less with the details. It scarcely seems 

 to matter whether the details of my paper are right or wrong, while the 

 conclusion is not denied. Whether Polyommalus Jiippothoe disappeared in 

 consequence of greedy collectors exterminating it, of the fens it inhabited 

 being drained and the food of the larvse destroyed, or of the larvae themselves 

 being drowned by a flood, is a matter of very little consequence so long as 

 we cannot dispute the lamentable fact that it has disappeared for ever. 

 Those who argue without practical result might show that man was responsible 

 m either of the above cases. But such an argument would not advance our 

 knowledge, and if we agreed that man had done it, the question of means 

 would still arise, and the actual cause would merit separate mention. Suppose 

 three different species had been lost, each by one of the above causes, it 

 it would be entirely misleading to say they had all been exterminated by the 

 action of man. But I would call Mr. Decie's attention to the title of my 

 paper in the March number (p. 59). I did not seek to enquire into the 

 cause of the disappearance of our butterflies, but whether any general diminu- 

 tion of their numbers was really going on. In going through the different 

 species I named, I merely referred to the facts of their disappearance from 

 various places, and scarcely ever to a cause for such disappearance. Certainly, 

 I did, in the last paragraph, mention f the cause generally assigned," but only 

 because the table given in the previous paragraph seemed to support this 

 generally assigned cause, and the whole subject was dismissed in a few lines. 

 Mr. Decie and Mr. Dale seem to think that I am wrong in accepting this 

 conclusion, and hold that human agencies have had much more to do with 

 what we all so much regret. Mr. Decie goes much into detail, and I cannot 

 but notice that while he is arguing that " the main cause of all permanent 

 disappearance of our butterflies is not the weather but mm, 3 ' he attributes 

 far more importance to the influence of the weather than he seems to be 

 aware of. Thus, in speaking of M. artemis he tells us that in his part " of 



