The colour of the male ranges from pale yellow ochre, through pale brown to reddish or dark brown; and in the female from pale brown to reddish brown; two cross lines are generally present on the fore wings; the space between the lines is usually darker in the female, and sometimes in the male also, forming a dark central band. All these colour forms were reared from some caterpillars taken by myself at Byfleet, Surrey, in 1901. Another year a few caterpillars taken at Esher produced ochreous coloured males and pale brown females only; the bands of the latter were narrower than usual and much contracted below the middle. As the females last mentioned are somewhat under the normal size I am inclined to think that the caterpillars from which they were reared had been on short commons during their last stage. Two males and a female are shown on Plate 48. The greyish brown eggs are laid during July and August in a ring cluster around a twig as shown on Plate 49, and so they remain exposed to all weathers during the winter. In April the caterpillars hatch out, and as they live in company throughout the greater part of their larval existence, the first business is to {108} construct a silken tent-like web (Fig. 22). The exterior of the tent affords a suitable surface upon which they can lie when they take a sun bath, which they seem fond of doing whenever the opportunity offers. It is also used, as well as the interior, for the process of skin-changing. [Illustration: FIG. 22. WEB OF LACKEY CATERPILLARS. (Photo by W. J. Lucas.)] The full-grown caterpillar is slaty blue above; along the middle of the back is a bluish white line, bordered on each side by a reddish-orange-lined black stripe; towards the lower limit of the slaty blue colour is a black edged reddish-orange line, and below this again the ground colour is flecked with orange, sometimes forming a line in the region of the spiracles; there are two velvety black spots on the back of the ring nearest the head, and a smaller black spot on each side of the next two rings; the hairs are brownish, rather more numerous on the sides than on the back. Head slaty-blue with two black eye-like spots. It feeds from April to June on hawthorn, sloe, and various fruit trees in orchards and gardens; also on birch, elm, oak, sallow, willow, etc. Chrysalis blackish, rather downy enclosed in a double {109} oval-shaped cocoon; the inner compartment is of rather closer woven silk, and is thickly covered with a yellowish substance, which is ejected by the caterpillar as a fluid, and afterwards drying forms a sulphur-like powder on the cocoon, and in a lesser degree on the chrysalis also. The moth is on the wing in July and August, but it is rarely seen in the daytime, and not often at night, except when attracted by light into the house, or to the gas or electric lamps. It is exceedingly easy to rear, either from eggs or from collected caterpillars; the latter are often abundant.