Colouring:—Upper side, dark blue, granulated with black scales that give it a dull aspect, having a black border, and a series of large black spots across the front wing. Under side, greyish drab, suffused with greenish blue near the body; towards centre, many black spots in indistinct light-coloured rings, and a double border of the same. No red spots.
The caterpillar is unknown.
The butterfly appears in July, frequenting rough, flowery pasture-grounds, but is exceedingly local. A famous place for it is Barnwell Wold, about a mile and a half from the village of Barnwell, near Oundle, Northamptonshire, where the insect was discovered by the Rev. W. Bree many years ago; but it is less abundant there than formerly, from the repeated attacks of collectors, who catch all they can find. Other localities, mentioned in various works, are—Brington, Huntingdonshire; Shortwood, and some other spots, near Cheltenham; Charmouth, Dorsetshire; Dover; Downs
near Glastonbury, Somerset; Downs near Marlborough, Wiltshire; Broomham, Bedfordshire; near Bedford; near Winchester.
THE CHALK-HILL BLUE. (Polyommatus Corydon.)
([Plate XIV]. fig. 2, Male; 2 a, Female.)
Colouring:—Upper side, male, pale silvery greenish blue, with very silky gloss, and shading off into a broad black border.
Female, dark smoky brown, with a leaden tinge, sprinkled near the body with greenish blue scales of the same colour as the males; border of orange spots, more or less visible. Under side marked as in fig. 2 a, on a brown ground, with a row of red spots near border of hind wing.
The caterpillar ([Plate I]. fig. 10) is green, striped with yellow on the back and sides.