Colouring:—Upper side, male, deep purple, or mazarine blue, with a border of black (fig. 5); female, dark brown (fig. 5 a). Under sides of both sexes similar, pale greyish drab, tinged at the base with greenish blue, numerous black spots in white rings. No red spots.
Though this elegant butterfly was frequently met with some years ago, it has lately become one of our rarest species, and I can give no locality where it can be now found. It has been reported as taken lately at Ventnor, Isle of Wight, and somewhere in South Wales, also in other places, but only singly.
Collectors, on visiting any new district, should net all the Blues they are not quite sure are common ones, and this may perchance turn up among them sometimes.
The caterpillar is said to feed on the flower heads of common Thrift (Armeria vulgaris).
The butterfly may be looked for in July.
THE LARGE BLUE. (Polyommatus Arion.)
([Plate XIV]. fig. 1.)
This is the largest of all our "Blues," and, next to the last, the rarest, though still taken in some numbers every year.