97 



tinct from our other species there is no doubt, for the superior wings 

 are formed more like those of Cerigo texta ( = Cerigo matura, Hufn., 

 = eytherea, Fb.), the stigmata are larger than those of T. orbona 

 (= comes), the fascia of the inferior wings is broader, and the supe- 

 rior margin beneath is black, not rosy." 



From these remarks it is evident that he compared it with our 

 ordinary South English forms, and no wonder the differences noted 

 were sufficiently convincing ; but how much more remarkable is the 

 difference between the South-east European forms and the extreme 

 forms from Orkney ? Not only is there a vast difference in orna- 

 mentation, but the European examples are considerably larger 

 and proportionately much more robust in structure than the 



Desquamated wings of TriphcBna comes. 



Asia Minor. Orkney. 



Orkney representatives. The desquamated wings now exhibited 

 show this very clearly ; and although there does not appear to 

 .be any actual difference in the venation itself, it is noticeably slighter 

 in structure in the Orkney insect, more particularly in the fore- 

 wings. 



In approaching the question of the probable line followed in 

 arriving at this remarkable form of variation, it may assist us if we con- 

 sider the matter under two heads, namely, retrogressive variation and 

 progressive variation. The running together of certain spots on the 

 under sides of the Lycsenidse, the appearance of unusual markings in 

 the members of some other groups, and similar phenomena gene- 

 rally accepted as cases of atavism,* do not appear to me to offer an 

 explanation in this instance. Such cases are generally of infrequent 

 occurrence, and in parallel forms of variation among members of 

 several nearly allied species, and are not necessarily confined to any 

 particular district ; but we do not find a similar form of variation to 

 that observed in co7?ies running through other members of the genus 

 TriphcBna, or of those of the large genus Agrotis, in which cot7ies is 

 now placed by many authors, nor have I been able to discover any 



* The Scilly examples already referred to may probably represent a case of 

 atavism ; the flouncing of the transverse lines is not infrequent in many of 

 genera of the Noctuse. 



