1 90 THE BOOK OF BRITISH BUTTERFLIES. 



The costal margin of the fore-wings of the imago 

 (Figs. 210 and 211) is straight, and the hind-margin of 

 both fore- and hind-wings rounded and entire. The fringe 

 is white, slightly marked with brown at the nervures. The 

 colour of the upper surface is dark sepia-brown. In the 

 typical form there is a black discoidal spot on the fore- 

 wings, and a row of red arched spots inside the margin of 

 all the wings. On the under-surface (Fig. 211) the ground- 

 colour is greyish-brown. Inside the margin comes a 

 row of black spots, edged with white externally and with 

 red internally. The red is bounded by black arches 

 edged with white towards the base of the wing. Within 

 this marginal black, red, and white band there are on 

 the fore-wings about seven white-edged black spots, and 

 on the hind-wings about a dozen. The white dash on 

 the hind-wings is conspicuous. This, the typical form, is 

 seen at its best on the downs in the south of England. 



As we proceed northwards, the black discoidal spot 

 on the fore-wings becomes surrounded with white, the 

 red spots grow less and less distinct, and gradually 

 disappear from the fore-wings, while the black centres to 

 the spots on the under-surface become smaller. At this 

 stage the little butterfly acquires the varietal name 

 salmacis, Steph. (Castle Eden Argus, or Durham 

 Argus). 



Proceeding farther north and crossing the Border into 

 Scotland, the red marks will be found to have quite 

 disappeared from the upper surface of the fore-wings, 

 and almost from the hind ones ; the discoidal spot on 

 the fore-wings is now pure white, and the under-surface 

 extremely delicate, for the black centres have altogether 

 disappeared from the white spots. We now have var. 

 artaxerxes, Fabr. (Scotch Brown Argus) (Figs. 212 

 and 213). 



