THE ENTOMOLOGIST. 



Vol. LII.] MAY, 1919. [No. 672 



THE VAEIATION OF SARROTHRIPUS REVAYANA, 



SCOPOLI. 



By W. G. Sheldon, F.Z.S., F.E.S. 

 (Plate I.) 



The geographical distribution and range of this polymorphic 

 species is at present very imperfectly known, because, although 

 it almost certainly is found over practically the whole of the 

 palsearctic area, with the exception of the Arctic regions, there 

 are forms inhabiting India and America which do not seem 

 separable from it. For this reason any attempt to deal with the 

 subject of its variation that I am able to make can only concern 

 European forms, and more especially those which are found in 

 the British Islands. 



S. revayana in our country assumes about thirty fairly 

 distinct forms, and there are one or two others which occur 

 in the surrounding Continental areas, but which are not found 

 with us. Of these, thirteen have had names given to them, the 

 remainder, up to the present time, being without any. 



The authors of these names, or most of them, considered 

 they were naming distinct species and not forms of one species ; 

 but unfortunately the bulk of the subsequent writers in dis- 

 cussing these forms have not taken the trouble to refer to the 

 original descriptions. Consequently the nomenclature of the 

 whole is at present involved in confusion. 



It is to correct these errors and to try to understand the 

 general aspects of the variation that the present paper is 

 written. 



The most ambitious attempt to deal with the variation of 

 a British Lepidopteron is probably the monograph of the late 

 J. A. Clark on Peronea cristana, which is to be found in the 

 'Entomologist's Eecord,' vol. xiii, pp. 227-229, 261-265, and 

 287-293. P. cristana has gone very far towards producing a 

 number of subspecies, the forms being remarkably constant 

 and clearly defined, and intermediate specimens comparatively 

 rare. This is not tlie case with S. revayana, for although some 



ENTOM. — MAY, 1919. K 



