156 BRITISH BUTTERFLIES. 



normal form, approaching in this respect nevada, and departing more 

 widely from manitoba.] 



Variation. — This is probably one of the most interesting species, 

 from the point of view of variation, in the superfamily. From the 

 limited standpoint of any particular country it would be considered a 

 non-variable species, but so wide is its distribution throughout the 

 PalaBarctic and Nearctic areas, and so widely different its environment 

 both as regards latitude and altitude, that minor variations have 

 become more or less fixed in certain districts, and these have been 

 largely described as distinct species by various authors. Within the 

 limits of the Nearctic area this variation is very considerable, and more 

 or less valid reasons have been brought forward for considering the 

 American forms specifically distinct. This view, however, is not gener- 

 ally accepted, and the few American examples in the British Museum 

 collection would not lead us to allow them distinction as species. In 

 our later considerations of the forms that have been described, we shall 

 separately consider the Palsearctie and Nearctic races. Of the general 

 variation of the species, Oberthiir notes (Etudes d'Ent., xx., pp. 38-39) 

 that the species varies considerably. On August 10th, 1895, it was in 

 great abundance on the sand-dunes of Miel-Pot, between St. Malo and 

 Cancale, and among others, a $ was captured with the apex of hindwings 

 a "gris de lin " tint instead of the ordinary greenish-yellow ; at the same 

 place a $ was taken in which the white spots on the underside were 

 much reduced, and others in which they were tinged with yellow. 

 Among specimens from various localities, Oberthiir further observes 

 that he has examples from Savoy similar to the catena from Siberia ; 

 others from the Taurus, where the race is very bright and clear both 

 on upper- and underside, etc. Dealing with the general variation of 

 the upperside tints, based on the European specimens examined, we 

 think the following covers the more usual forms : 



1. Bright fulvous, almost unspotted (slight traces only towards apex of fore- 

 wings) ; usual marginal border almost obsolete = ab. clara, n. ab. 



2. Bright fulvous, marginal border fuscous, spotting on fore- and hindwings 

 faint = ab. intermedia, n. ab. 



3. Bright fulvous, marginal border and basal area fuscous, spotting pale 

 and conspicuous — comma, Linn. 



4. Ground colour suffused with fuscous, the fulvous restricted to the angulated 

 row of spots and discal cell on forewings ; and to the transverse row of spots and 

 discal spot on hindwings = ab. sufusa, n. ab. 



5. As in 4, but the spots yellowish, even whitish towards apex of forewings = 

 ab. pallidapuncta, n. ab. 



6. Almost entirely fuscous, spots much reduced on forewings, almost absent on 

 hindwings = ab. extrema, n. ab. 



Pathological aberrations, in which the pigment partially fails, and 

 the wing, or part of it, becomes pallid, sometimes occur. We have 

 four such, two J s in which the left hindwing is pale, one $ in which 

 both hindwings are pallid, and a $ the left hindwing pallid ; the latter 

 has a large pallid patch also on the underside of each forewing at anal 

 angle, not noticeable on upperside. Parsons records (ZooL, 1862, 

 p. 8204) that, in early September, 1862, he captured, at Aylesbury, an 

 example with its forewings milk-white, the hindwings of a delicate 

 green colour, the silvery spots of the underside shining through like 

 gold. In Britain the common $ form appears to be that noted above 

 as the type, whilst the $? is dimorphic, one form coloured correspond- 

 ingly with tbe type, the other ab. sufusa. Occasional $ s, however, 



