THE YOUNG NATURALIST, 



131 



one of our rarest natives." The supposition therefore, is that its rapid dis- 

 appearance has only lately begun, otherwise it would long e'er this have 

 entirely disappeared. Consequently it is hard to believe that the climate, 

 which has for this last thousand years, at least, remained partially unchanged, 

 can have been the cause of it. At all events the climate can hardly be held 

 directly responsible for its disappearance from fields at Penarth, near Cardiff, 

 which are now built over. 



2. Lyc^na Arion. — I have looked through the account of the partial 

 disappearance of this butterfly in the last volume of the E. M. M., and I find 

 that from a locality at Bolthead where it was once found it has definitely 

 disappeared. The reason of this disappearance is not far to seek, and we 

 have no need to fall back upon the climate. Man has changed the whole of 

 the face of the spot where the insect was formerly found, and by his innova- 

 tion has made it no longer a fit habitat for the species. The remainder 

 of the notes point to the fact that in many of its old localities the 

 species has not been seen since '77. But inasmuch as it still exists in 

 Devonshire, and its range widens or contracts according as the summers are 

 fine or the reverse, we may confidently expect that in the next few summers, 

 which it is generally admitted are likely to be propitious, it will once more 

 spread over many of its old haunts, as it seems to have spread over the 

 Cotswolds during the years between '66 and '70. 



3. Tkecla Pmni. — I do not personally know anything about this species. 

 Mr. Eobson himself seems rather uncertain to its right to the place which he 

 gives it in this class, and I should like to know on what evidence he has 

 given it this place. 



V. Species whose range is becoming restricted (11.) 

 The heading of this class points to a fact which, I think, tells not a little 

 in favour of my contention, a fact pointed out by Mr. Eobson on page 6.2, 

 when he says the species in this and the preceding class " which, common 

 where they occur, are disappearing from extensive tracts, and not again 

 spreading over them." I do not, of course, mean to say that I agree with 

 any such sweeping statement as that which Mr. Eobson makes there, but the 

 fact to which I refer lies embedded in that statement, and is this : — When a 

 species of butterfly begins to disappear, it does not do so by becoming rarer 

 all over the country ; but, while it remains in some places as numerous as 

 ever, in others it suddenly becomes scarce, or absolutely extinct, and this, 

 although all the places may be exposed to the same atmospheric influences. 

 This is not at all what we should expect if the disappearance was caused by 

 the influence of climate. Some other deeper cause must be locked for, a 



