THE EMPEROR MOTH (_Saturnia pavonia_).
In a general way the fore wings of the male may be described as purplish
grey, suffused with rosy or with tawny shades; a reddish cloud, black
marked above, at the tips of the wings; the outer margins are more or less
whitish, and there is a whitish patch about the middle of each wing, in
which is an eyed spot; the hind wings are tawny, with a central eye spot
and a blackish band towards the outer margin. The female has all the wings
pale purplish grey, with whitish bordered outer margins; markings much as
in the male, but the central area of the hindwings is more or less whitish.
There is some variation in the ornamentation; occasionally the white
markings are of large size, or, on the other hand, may be almost or quite
obscured. Very rarely the eye-spots are absent from all the wings (ab.
_obsoleta_, Tutt), and sometimes they are of abnormal shape. Now and then
specimens of the female sex are dark in colour, with red bands, and Barrett
mentions an example of this sex smoky black in colour, with still blacker
markings (Plate 66).
The olive brown, clouded greyish eggs are laid in neatly arranged batches
around the stems or twigs of plants; I once found a batch in North Devon on
a loose piece of rock. The caterpillar when full grown is bright green,
with black markings; the warts from which blackish bristles arise are
yellow, sometimes pink or blackish. In an early stage it is black, with an
orange line low down along the sides; later on it is still black, but
ringed with orange. It feeds in June, July, and August on many kinds of
plants, among which may be mentioned heather, bramble, sallow, sloe; also
meadow-sweet (_Spiræa ulmaria_) and purple loose-strife (_Lythrum
salicaria_).
The curious cocoon formed by the caterpillar (Plate 67) is {132} so
constructed at the narrow end that the moth on emergence can easily pass
through; after the insect's escape, the converging fibres forming the
"door" spring to again, and the point of exit looks pretty much as before
the moth had pushed through. This kind of opening can only be worked from
the inside, therefore enemies from without are unable to effect an
entrance.
The moths are out in April and May, and the males may be seen on sunny days
flying at a great pace over heaths, moorlands, and mosses, also about the
borders of woods. The female flies at night, but it may occasionally be met
with resting on heather or other herbage in the daytime. A freshly emerged
female moth will, as a rule, attract as many specimens of the opposite sex
as one would care to take; all that one has to do is to take her in a box
to some likely spot, and there await the coming of the males.
The species seems to be generally distributed throughout the British Isles,
but is commoner in some parts than in others, and apparently rare in
portions of the Midlands.
The distribution abroad extends through Europe to North Asia Minor and
Armenia, and to Siberia, Amurland, and Ussuri.