PLEBEIUS ARGUS. 169 



Imago. — 20mm. -35 ram. in wing-expanse. $ , All wings blue, with 

 a more or less well-defined dark marginal border, the fringes white ; 

 2 fuscous, with a more or less defined marginal series of orange 

 lunules on the hindwings, sometimes continued on the forewings, 

 the fringes grey. The underside with a discoidal lunule, a transverse 

 submedian elbowed series of dark white-margined spots, a marginal 

 series of dark spots edged internally w T ith yellow lunules, followed 

 by a pale band between these and the discoidal spot, on each wing ; 

 on the fore wing no spots between the discal lunule and base, on 

 the hindwing one or more spots between discal cell and base. The 

 black marginal spots near the anal angle of hindwing With metallic 

 silver-blue kernels. 



Sexual dimorphism. — The coloration of the sexes is entirely different 

 on the upperside, tbat of the $ being blue, with a dark marginal 

 border of varying width to the wings, the fringes white ; that of the 

 ? deep fuscous-black or fuscous-brown, with or without a marginal 

 series of orange lunules to the hindwings, less often to the forewings, 

 the fringes grey. On the underside the ground colour is also quite 

 different in the sexes, that of the $ being distinctly paler than tbat 

 of the ? , and in some of the local races showing a very great differ- 

 ence ; in the var. hypocliiona and var. bejarensis the colour of the under- 

 side of the $ is of an extremely white (or bluish-white) tint, that of 

 the $ s brown, the usual white submedian band being reduced to mere 

 pale lunules on the hindw T ings. The spots on the underside are usually 

 larger in the £ (sometimes much larger), and hence often appear much 

 more crowded and closer to the discoidal spot in both fore- and hind- 

 wings ; the orange markings on the underside are usually more strongly 

 developed, and the tint more intense in the 2 s than in the $ s. In 

 almost all the races of this species, the average wing-expanse of the 

 $ appears to be greater than that of the ? , but Kebel notes that, in the 

 Bulgarian race, the $ s vary from 20mm. -23mm., and the $ s from 

 22mm. -25mm. The scaling of the sexes is described (in litt.) by 

 Pierce as follows: $ . — (1) Transparent scales -0035m. x -0015m., 

 yellow in colour, plain at apex. (2) Dark scales -005in. x 'OOlin., 

 apex with three and four points. (3) Androconia -0028in. x -OOlin., 

 oval in form, the ends being rounded ; each with eight rows of nine or 

 ten spots each, connected longitudinally by a line. (4) Underside 

 scales typical, three- or four-pointed at the apex. 2 . — (1) Dark scales, 

 typical, but with five small, even points. (2) Transparent yellow 

 scales present in the blue-tinted 2 s only ; these scales are usually 

 plain at the apex, but sometimes three- and occasionally five-lobed* 

 (3) Underside scales of typical form, but with five deeply-emarginate 

 points. $ and $. — The "silver-studded" scales are transparent, deeply 

 scored with coarse strias, which cause them to appear pinky-blue ; the 

 apex not deeply four-lobed. The androconia are described by 

 Aurivillius (Bihang till k. Svensk. Vet. Akad. Handl., v., no. 25, pp. 25- 

 26) as " tolerably elongated, elliptical,* with eight to nine rows of 



* Aurivillius notes (op. cit.) that "the androconia of P. argyrognomou are 

 very dissimilar to those of P. argus (aegon), being almost circular, 0054mm. in 

 width, with ten to twelve rows ot dots thereon; the hair-scales very numerous, par- 

 ticularly in the outer parts of cells one to three ; by this character and the forma- 

 tion of the androconia, this species is easily distinguished from P. argus (aegon). 

 Even with a moderate magnifying-glass the hair-scales may be easily recognised 

 as white hairs." 



