THE CHALKHILL BLUE 
227 
Female. The colour here varies from deep dusky-brown =ab. 
iphis, to all blue except the marginal orange spots and dark 
borders. Every gradation of intermediate form occurs 
between these two extreme types. The tint of blue varies 
through all shades of purple, violet, and blue. In some 
specimens the margins of the hind wings are bright blue, which 
colour surrounds the orange spots, producing a beautiful com¬ 
bination of colour. Sometimes both fore and hind wings have 
the discoidal spots surrounded with white ; frequently whitish 
or pale blue wedge-shaped markings run from the margin to the 
centre of the hind wing and are found on the apex of the fore 
wing. Occasionally, the orange marginal spots on both surfaces 
are replaced by very pale yellow, and in still rarer cases by 
chocolate-brown. The spotting on the under surface is subject 
to extreme aberration. At times the whole of the under side 
is free from spots except for the outer marginal spots ; this 
is known as ab. persica ; in others the spots form streaks = 
ab. striata . A fairly common type of aberration is when the 
two lowest spots on the fore wing are united to form a curved 
bar=ab. arena ; sometimes similar marks occur on the hind 
wings. Occasionally examples having one side of normal 
colouring and markings and the other side very variable have 
been found. Many Scotch and Irish specimens are very 
large and brilliantly coloured. Gynandromorphism appears 
more frequently here than in any other British butterfly ; 
except, perhaps, the Silver-studded Blue. 
Genus LYSANDRA, Hemming , 1933 
THE CHALKHILL BLUE 
Lysandra coridon (Poda, 1761). 
(Plate XIX, facing page 208) 
This is a locally-abundant and beautiful butterfly, whose 
remarkable colouring distinguishes it at a glance from any 
other British species. The cold, silvery, pale blue hue 
resembles the tint of a cloudless summer evening sky. It is 
a colour of rare occurrence in nature. 
