256 THE ENTOMOLOGIST. 



is exactly identical with certain British viburnana, which are 

 probably not very unlike the specimen of donelana resembling 

 viburnana referred to by Mr. Carpenter. 



Richard South. 



THE DIAMOND-BACK MOTH {PLUTELLA CEUCIFERARUM). 



By J. Arkle. 



Although the year 1891 has not been marked by the appear- 

 ance of attractive and welcome insects, such as Colias edusa or 

 Deilephila galii, it may be handed down to entomological posterity 

 as celebrated for the occurrence of a moth which, if diminutive 

 in size, brought itself into prominent notice by its pestiferous 

 abundance. Happily, it may be added, manj'^ entomologists, at 

 any rate in western Britain, are unacquainted with this little 

 turnip moth, which has shown a power, during the past summer 

 months, to work destruction from the shores of the Forth to 

 those of The Wash. It is the Cerostoma xylostella of Curtis — 

 not, it may be observed, the beautiful hook-tipped C. xylostella 

 of Stainton — the Harpipteryx xylostella of South ! In the genus 

 Cerostoma, Stainton describes the pupa as being enclosed in a 

 close, firm cocoon; while, as we consider this matter of synonyms, 

 it is worth noting that his adopted Plutella is distinguished by a 

 cocoon of open network. Mr. South also adopts Plutella in his 

 ' Synonymic List,' and, in common with Stainton, he uses the 

 appropriate specific name of cruciferarum. 



Although this insect-pest occurs more or less, year after year, 

 in the infected districts, the question naturally arises — What is 

 the reason of its extraordinary abundance this season ? Possibly 

 it may be as mysterious an apparition as C. edusa or D. galii — 

 or the advantages in aid of hybernation may have been exceptional 

 during the winter — or it may have come to us from across the 

 sea ! The migratory, or blown-over, theory may receive some 

 support from the following story, which I take from ' The Liver- 

 pool Daily Post' for Aug. 15th : — " Mr. H. A. Paynter, solicitor, 

 Alnwick, told Mr. Eaynard, Inspector of the Board of Agriculture, 

 that, being requested by Lord Walsingham to try and get him 

 some moths, he (Mr. Paynter) proceeded, on July 10th, to the 

 Longstone Lighthouse, on the Fame Islands, where he found the 

 rocks close to the lighthouse covered with them. On questioning 

 the three lighthouse-keepers upon this remarkable occurrence, 

 they informed him that such a great cloud of moths was driven 

 over by the north-east wind that they were obliged to keep 

 sweeping them oif the lantern throughout the whole night in 

 order to allow the light to be seen at sea." The paragraph then 

 goes on to say that "this statement made by the lighthouse- 



