278 BRITISH BUTTERFLIES. 



discoidal lunule and outer margin of forewings, edged internally with 

 darker ; the hindwings with two white transverse lines, the inner 

 incomplete, the area between these sometimes rather darker; a reddish 

 marginal band ; a small black spot at anal angle, and another at base 

 of "tail" of hindwings. 



Sexual dimorphism. — No specialised androconial scales have been 

 yet discovered in the males of this species, but there are marked 

 sexual differences in the colour and pattern. On the bpperside the most 

 marked difference is the presence of a well-developed, transverse, 

 orange band, situated just outside the discal area. Aurivillius 

 describes it as " normally occupying the centre of the second and 

 third wing-cells, the entire inner half of the fourth and fifth, and the base 

 of the sixth and seventh, besides forming a spot in the outer part of 

 cell B." Apart from the conspicuous orange band of the forewings, 

 the tails of the hindwings are usually somewhat better-developed in 

 the female than in the male, whilst the ground colour of the under- 

 sides of all the wings is usually markedly brighter and more intensely 

 coloured in the female than in the male, particularly is this the case 

 in the marginal orange-red band of the hindwings, which is, in the 

 female, often continued on the forewings. In ehcesi, if this be con- 

 sidered a variety of this species, the sexual diversity is still more 

 marked, for, in this form, the whole of the four wings, except for the 

 apical patch and outer marginal band of the forewings, is wholly orange. 

 The variation in the colour arrangement in both sexes is dealt with 

 infra, pp. 278-279. Of the European examples, Heron notes the 

 smallest male in the British Museum collection as 40mm., the largest 

 44mm. ; the smallest female 37mm., the largest 42mm. These 

 measurements seem somewhat above the average. 



Gynandromorphs. — The following are the only specimens of which 

 we have knowledge : 



a. Perfect gynandromorpli. Right side <? , left $ . The sex characters sharply 

 divided in form, coloration, and markings of the wings as noted. The orange-red 

 spot of the forewings very bright on the left side, the costa and hind margin reddish 

 tinted. Left antenna rather shorter than right. The abdomen in shape strongly ? . 

 The left wings shorter (19mm.) than the right wings (30mm.). Bred at Hamburg, 

 1897 (Wiskott, Iris, x., pp. 379-380). 



j3. A perfect gynandromorph. Right side ? , left i . Bred at Eperjes, in 

 Hungary, August 11th, 1876. The right ( ? ) side has a large orange spot ; on the 

 undersides the colour of the ? side also shows the sexual difference, being of a 

 much brighter colour than the c? side. The example is now in the Hungarian 

 National Museum (Aigner-Abafi, in litt). 



Variation. — There is considerable variation in the colour and size 

 of Ruralis betulae, and, if crassa, Leech, and elwesi, Leech, be included 

 as having only varietal rank, the size variation is indeed remarkable. 

 Leaving these two forms for later consideration, the examples in the 

 British Museum collection give the following range of variation on the 

 upperside in the different sexes : 



I. Males— 



1. Entirely fuscous with no pale patches on forewings =unicolor, n. ab. 



2. Entirely fuscous except for a pale orange shade on the outside of the 



discoidal lunule = ab. subwiicolor, n. ab. 



3. Fuscous with pale orange shade outside discoidal lunule and continued 



series (two) of pale orange interneural dashes below = ab. xpinosae, 

 Gerh. 



4. As in 3, but the paler areas faintly yellowish = ah. lutca, n. ab. 



5. As in 3, but the paler areas faintly grey = ab. grisea, n. ab. 



6. As in 3, but the paler areas whitish = ab. pallida, Tutt. 



