'^- NOTES AND COMMENTS. 653 



In the last part of the Ann. Set. Nat. Zool. (vol. xiii., Nos. 4, 5, 

 1892), Messrs. Milne Edwards and E. L. Bouvier complete their 

 description of the Pagurus-Vike crustaceans of the deep sea. It is 

 ■well-known that the submerged mountain-chain extending north and 

 south in the Atlantic — the chain of which the Azores, St. Paul, and 

 Ascension are isolated peaks — forms a division between two distinct 

 faunas on the bed of the ocean ; and the difference between the 

 Paguridae of the two sides proves to be very marked. 



Mr. Clement Reid favours us with an interesting note on the 

 "Cheese Snail." This species, Helix obvoliita, is often spoken of as a 

 doubtful native of Britain, and in most books it is said to be con- 

 fined to a small portion of the chalk escarpment on the borders of 

 Hampshire and Sussex. The species is, however, abundant in all 

 suitable localities in Sussex, as far east as the river Arun, and its rarity 

 is due to the rarity of suitable stations. Helix obvolnta is extremely par- 

 ticular as to its habitat, needmg shade, with a dry calcareous soil 

 and a steep slope. It appears, also, to have exceptionally small 

 facilities for dispersal, for it is almost entirely confined to the few 

 remaining patches of woodland and copse which have never been 

 under cultivation, and is absent from the extensive beech woods 

 planted a centur}'^ ago. As the occurrence of this typical woodland 

 species seems intimately connected with the survival of patches of 

 the ancient forest, it should be carefully searched for in- other counties 

 where suitable conditions occur. In all probability. Helix obvolnta 

 is less local than is imagined. 



The year 1892 has been a noteworthy one for Lepidopterists, on 

 account of the abundance of the Clouded Yellow Butterfly, Colias edusa, 

 in Great Britain. Records of its occurrence in many counties have 

 been published in the entomological journals. This species and its 

 congener, C. hyale, are well known to be numerous in Britain at 

 irregular intervals, and the cause of their sudden appearance and 

 disappearance has long been a puzzle. In his work on the British 

 Lepidoptera, now appearing, Mr. C. G. Barrett inclines to the view 

 that pressure of numbers on the continent causes a migration to our 

 shores, and that many of the migrants establish themselves and breed 

 here. The present is said to be the best " edusa year " since 1877. 



The discovery of the host of the rare Stylopid insect Elenchus 

 teniiicornis is announced in the Entom. Monthly Mag. (2), vol.iii., p. 249, 

 by Mr. E. Saunders, who captured near Surbiton a nymph of a small 

 Homopteron {Libiivnia, sp.) from the ventral region of whose abdo- 

 men a male Elenchus was in the act of emerging. It has hitherto 

 been believed that Elenchus, like most other Stylopidas, was parasitic 

 on bees, and species of Bombus have been thought to be its hosts. 



