1886. 213 



in my cabinet as that species, where they have remained ever since. Although I 

 have twice come across the larvae of Gel. malvella feeding in autumn, I have always 

 failed to breed them. 



This last autumn, however, I received a few bred Oel. malvella from Mr. E. R. 

 Bankes of Corfe Castle, with which I hoped to complete my series. When, how- 

 ever, I came to compare them, I observed at once that these bred specimens were 

 darker than my old ones, with the dark fascia much more clearly expressed ; and, 

 on further examination, I found that my old specimens were in reality not malvella 

 at all, but vilella, Z., the black dot at the base of the inner margin, which I had 

 failed to notice before, being conclusive. I am not aware if Gel. vilella has been 

 recorded as bred, but am under the impression that it has not. Whether the larvae 

 I found had really fed on the mallow or on some other plant I cannot say ; but if, 

 as I believe, the imagos of vilella hibernate, and can be beaten from thatch in 

 spring, these larvae must have fed up the same summer. I hope, if all's well, during 

 the coming season, to renew my acquaintance with the larvae so unfortunately un- 

 recognised 15 years ago. — W. Waeeen, Merton Cottage, Cambridge : January 

 12th, 1886. 



Distribution of Lepidoptera. — Mr. Barrett, in his last month's note on this 

 subject, has touched upon a very interesting question, and one which so far has not, 

 to the best of my knowledge, been sufficiently investigated. Surely many Entomo- 

 logists residing for many years in the same neighbourhood can call to mind numerous 

 instances of iluctuation in the distribution of insects : not only that they may by 

 chance capture a single specimen unknown in their district before, not only that 

 certain insects are common one year and scarce the next, but what is far more 

 interesting, that certain insects apparently become more abundant at the expense of 

 others, and gradually spread by what appears to be a slow migratory wave from one 

 locality to others. 



I am not here speakingof the sudden appearance and equally sudden disappearance 

 of such insects as Colias Edusa and Vanessa Antiopa, which, probably owing to their 

 strong powers of flight, brilliant appearance, and numbers, thrust themselves on our 

 notice and compel our admiration while we confess ignorance of the cause, but I 

 refer to the slower and less obtrusive manner in which many so-called local insects 

 change their metropolis from year to year, and become common where they were 

 formerly unknown. 



To explain my meaning further, I will example Thecla to-album, MelitcBa 

 Artemis, and Arge Galatea, which have come more especially under my notice at 

 Marlborough, where the entomological records of the College go back for twenty 

 years, and my own observations incorporated with the above for twelve years. 



Thecla w-album is, I imagine, a typical local insect, and we had no record of its 

 occurring at Marlborough until 1873 ; 8 years after accurate records were com- 

 menced, when in the August of that year it was taken sparingly by Mr. Meyrick, 

 and singly by myself, in localities some miles distant from each other, but both east 

 of the town. In July of the following year, I discovered what may be called their 

 head-quarters, midway between the localities of the year before, and here they were 



