idice) near the _centre_ of the front wings; _beneath_, a white
ground, with green marblings, that are much more sharply defined than those
in _Daplidice_. Near the centre of the front wing is a _clear black spot_,
corresponding in position with that on the upper surface, _and not shaded
off with green, as in Daplidice_.

We speak of the _green_ marblings of this species--and, to the naked eye,
they do appear to be of quite a bright green--but under a microscope or
powerful lens that colour disappears, being resolved into a combination of
bright yellow and pure black scales, which, with the dazzling snow-white
ground scales that surround them, form a microscopic tableau of
extraordinary beauty. This can, however, only be seen by daylight, for
under artificial light the yellow, on which the whole effect depends, is
entirely lost.

The _caterpillar_ is slightly hairy, and green, with a white stripe on each
side. It has been generally stated that the _Cardamine impatiens_ is the
common food plant of this species, _apropos_ of which I will quote the
following communication from Mr. Doubleday to the editor of the
_Zoologist_:--

"In reply to your query about the food of the larva of _Cardamines_, I may
say that I have found it upon several plants. I believe that _Cardamine
pratensis_ (common cuckoo-flower) is the one on which the eggs {93} are
most frequently deposited, but the greater part of the _larvae_ must perish
in this neighbourhood, because the fields are mowed before the larvae are
full-grown. I have very often seen the larvae on the seed-pods of _Erysimum
Alliaria_, and have several times found the _pupae_ on the dead stems of
this plant in winter; I think that it is the principal food of Cardamines
at Epping; it also probably feeds on _E. barbarea_, and other similar
plants. Some years ago we used to have a quantity of a large single rocket
in the garden, and there was always a number of the larvae of _Cardamines_
feeding on the seed-pods. _Cardamine impatiens_ is so local a plant _that
it cannot be the common food of the larvae of Cardamines_."

The _chrysalis_ is of the very singular shape shown at fig. 17, Plate I., a
shape quite unique among British butterflies, though that of the next
slightly approaches it. It is to be looked for in autumn and winter on the
dry, dead stems of the plants named in the foregoing paragraph.

The perfect butterfly, which is very common throughout the country, is met
with from