es," though some of them are _not blue_ at
all. In their manners, and the localities they inhabit, there is so much in
common, that one description of these will answer for nearly every one of
them; so that my small available space will be in great part devoted to
pointing out the marks of distinction between the various species, ten in
number, several of them closely resembling others in general appearance,
and requiring some care in their discrimination.

Their _caterpillars_, which are wood-louse shaped, or _onisciform_,
generally feed on low plants, chiefly of the papilionaceous order; and the
_butterflies_ are found in dry meadows, on downs, and in open heathy
places. The first species, _P. Argiolus_, is, however, an exception to the
above, both in its food and haunts. {151}

Several species of this genus are often found together. For example, in the
Isle of Wight, last August, I took _P. Argiolus_, _Corydon_, _Adonis_,
_Alexis_, and _Agestis_, all within about one hour, and a space of a few
yards square in the corner of a field.

* * * * *

THE AZURE BLUE BUTTERFLY. (_Polyommatus Argiolus._)

(Plate XIII. fig. 3, Male; 3 _a_, Female.)

_Colouring_:--Upper side, beautiful lilac blue--the male with a narrow
black border (fig. 3), the female with a broad one, sometimes extending
over the outer half of the wing (fig. 3 a). Under side, very delicate
_silvery blue, almost white_, with numerous small black spots. _No red
spots._

_Caterpillar_, green, with darker line on back. Feeds on the flowers of
holly, ivy, and buckthorn.

The _butterfly_ appears in May, or sometimes in April, and again in August,
frequenting _woods_ and hedges, especially where holly and ivy abound. I
noticed immense numbers about the ivied walls of Chepstow Castle.

As the name "Azure Blue" is in general use, I have retained it above, but
that of "Holly Blue," sometimes {152} applied to it, is preferable, as its
colour is much less an azure blue than that of _Adonis_.

Localities:--Common in the south, and found as far north as Durham and the
Lake District. Not known in Scotland.

* * * * *

THE BEDFORD BLUE, OR LITTLE BLUE. (_Polyommatus Alsus._)

(Plate XIII. fig. 4, Male; 4 _a_, Female.)

This is the _smallest of British butterflies_, specimens being sometimes
seen even smaller than those figured.

_Colouring_:--Upper side, dark brown, distinctly powdered with blue n