The males fly in the sunshine, and are very strong on the wing; the females are not active until dark. This sex has been found resting on the twigs of birch, also on heather, and occasionally on a tree trunk. The males "assemble" freely to a freshly emerged female. The species inhabits the more open parts of woods and forests, moors and hillsides where birches flourish. It is probably more plentiful in its Scottish localities, such as Rannoch and Forres, than elsewhere, but it occurs also in Aberdeenshire, Kincardineshire, and Argyllshire. In England it seems to be not uncommon in Wyre Forest, Worcestershire, and the Reading district in Berkshire. It used to be so plentiful in Tilgate Forest, Sussex, that over a hundred males were brought to the net in one day by a bred female put down to allure them. This happened some fifty years ago, and compares curiously with a record of one male attracted by a female in Tilgate Forest, April 13, 1869. Other localities in Sussex that have been mentioned are St. Leonard's Forest and near Petersfield; it has also been found in Herefordshire and in some parts of Suffolk. Distributed over Central and Northern Europe, the range extending to North Italy. [Illustration] Pl. 66. 1, 2. EMPEROR MOTH, _males_; 3 _female_. [Illustration] Pl. 67. EMPEROR MOTH. _Eggs, natural size and enlarged._ _Caterpillars and cocoon._ (_Photos. by W. J. Lucas._) {131} SATURNIIDÆ. 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).