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THE YOUNG NATURALIST. 



cause, which will hardly ever be found to be the same in any two cases, a 

 cause which, in all probability it will be no easy matter to discover. It is 

 really a most unfortunate thing that, with regard to all the species falling 

 under this important head, Mr. Eobson has made his remarks "as brief as 

 possible." So brief, indeed, are they, and to such a small extent do they 

 support the meagre information to be found in the books, that I am unable 

 even to guess at the causes of the alleged disappearances of many of the 

 species. This is notably the case with P. cratagi, A. aglaia, S, cegeria, 

 C. pamp/iilus, L. alsus, and P. p7ilczas. I can only hope that on some future 

 occasion Mr. Eobson may find an opportunity to tell us something more 

 about these butterflies. As to the few 'remaining species I would like to say 

 a few more words : — 



1. Papilio Machaon. — This species has certainly a range very much 

 more restricted than that which it once had. I am unable to suggest any 

 probable cause for its now confining itself to the fens, but I think Mr. Eobson 

 will find it hard to show that its limited range is the effect of the malignant 

 influence of climate, at all events its disappearance from its old haunts in the 

 suburbs of London is easily explained, man the collector, and man the builder 

 have exterminated it or driven it away, Some of its old haunts are now 

 entirely built over, and in the others a conspicuous and handsome insect like 

 Machaon w T ould soon be made an end of by the crowds of little boys and 

 entomologists (so-called), who are always ready about to catch and kill every- 

 thing, whether they really want it or no. 



2. Vanessa C- album. — Here, again, climate has had little or no influence. 

 What is the cause of this species now confining itself to the hop-growing 

 counties I cannot say, but I should think that its reported present scarcity 

 in Kent is produced by the increase of hop washing in that county. Here 

 the hops are washed comparatively little, and though the insect is, as it always 

 has been, very variable in its numbers from year to year, it shows no signs of 

 permanent decrease ; it is a marvel to me that it does not do so, for the 

 destruction of pupse that takes place during the hop picking season every 

 year is simply apalling. I do not understand how any escape. Escape, 

 however, some certainly do, and the wonderful vitality and fecundity of the 

 species enable it to remain tolerably numerous. 



3. M. Artemis. — I think that I shall be able to show that in most 

 cases, at all events, the disappearance of this species is caused by man, and in 

 this part of the country bad seasons have been positively beneficial to it. The 

 larva feeds principally (I believe here exclusively) upon the Devil's-bit 

 Scabious. Where a good system of drainage and tolerably good farming are 



