398 BRITISH BUTTERFLIES. 



female (taken at Geneva, in May) , which has the two black spots of the 

 median series, on the underside of the hindwings, i.e., those nearest 

 the anal angle, united, so as to form a reversed letter C, strongly 

 marked, and of a deep black colour (in coll. Samson) ; another in his 

 own collection taken at the foot of the Saleve in May, presents the 

 same peculiarity, but less marked = ab. c-nigrum, n. ab. The underside 

 variation in the spotting may be roughly classified as : 



1. Without any of the transverse row of dots or basal dots 



or marginal lunules « = ab. obsoleta, n. ab. 



2. With only faintest traces of a few dots =ab. hypoleuca, Koll. 



3. With minute dots but no marginal lunules = argiolus, lAm\.(parvi- 



puncta, Fuchs). 



4. With minute dots and streaks, and traces of marginal 



lunules = Sub. argyphontes, Bergs. 



5. With a dark disc to forewings, a transverse rows of dots, 



but no marginal lunules =ab. argalus, Bergs. 



6. With a well-developed row of dots and streaks, but no 



marginal lunules =ab. transversa, n. ab. 



7. With a well-developed row of dots or streaks, and 



marginal lunules =ab. cleobis, Sulz. 



8. With a well-developed row of pale-ringed dots and 



streaks, but no marginal lunules =ab. albocincta, n. ab. 



9. With a well-developed row of pale-ringed dots and 



streaks, and marginal lunules =ab. albocincta-cleobis, 



n. ab. 



Sulzer described (Abg. Ges., p. 146, pi. xviii., figs. 13-14) a strongly- 

 spotted $> form as cleobis, his description reading: "Blue, towards the 

 outer edge black, margined with white ; on the forewings towards 

 the costal edge, a small black hook ; a similar one towards the hind 

 margin of the hindwings ; the underside silvery-white, the forewings 

 with five, the hindwings with eleven black spots; Switzerland." 

 The underside of this species varies in its ground colour. Possibly 

 our British examples are more tinged with blue than those of any 

 other district, although some are silvery-white with very little blue 

 suffusion. As we go east, however, this suffusion appears to become 

 smaller, and those from Asia Minor are already quite grey, with 

 scarcely any trace of blue. In Asia, the spring forms are grey, the 

 summer often particularly white, whilst in America, the white or grey 

 ground is strongly dusted with fuscous and black, especially in the spring 

 examples. Still, here some trace of blue is occasionally noted by authors. 

 It may be well now to note the original descriptions of Bergstrasser's 

 named forms, before dealing with the other named races and forms 

 arranged geographically. Bergstrasser's descriptions read as follows : 



a. ab. thersanon, Bergstr., "Nom.," iii., p. 4, pi. xlix., figs. 5-6 (1779); Bkh., 

 " Naturg.," etc., i., p. 174 (1788). — P.P.R. alis rotundatis integerrimis cserules- 

 centibus, fimbria alba, virgulis nigris ex adverso in disco utrimque binis ; subtus 

 solitario lineolarum punctorumque nigrorum ordine. Unicolorous blue wings with 

 white border, and comma-like mark in the centre of each wing ; the underside 

 pale bluish with a single arcuate row of black lines and dots. This insect on the 

 underside is very similar to the ? " buckthorn butterfly " (argiolus), but is without 

 any trace of the black marginal lunules, which are, in the latter, very pale, and 

 appear as if they were showing through from the upperside. Is this the c? of the 

 "buckthorn butterfly" (argiolus, Nom., pi. xlv., figs. 7-8)? Its size need be no 

 bar, for one finds ? s larger and as pale-margined as those figured (Bergstrasser). 



This is a form, whose special character is a faint discoidal lunule 

 showing on the disc of the upperside of each wing. This is most 

 unusual in our Palaearctic examples, but is mentioned by Boisduval 



