The caterpillars of _Cerura_, _Dicranura_, and _Stauropus_ have the hind claspers transformed into tail-like appendages, which in the case of the Puss and Kittens take the form of a pair of slender tubes furnished with flagellæ, or whips, which can be protruded or withdrawn as occasion may require. These organs are presumably for defensive purposes, but are not always effective in combating the attack of parasitical flies, as these evidently manage to deposit their egg on the caterpillars not infrequently. The pupa, or chrysalis, of some kinds is enclosed in a hard cocoon on tree trunks, and others in a soft cocoon generally underground; sometimes, however, the cocoon is spun up between leaves; occasionally, as for example that of the Buff-tip, the chrysalis is found in the ground without any protecting covering, although the cell in which it was formed may have been flimsily lined with silk. Nearly one hundred species are referred to this family in Staudinger's "Catalogue of Palæarctic Lepidoptera," and of these twenty-five occur, or have been taken, in the British Isles, nearly all of which are accepted as indigenous. Two of the {58} three species not generally regarded as true natives have been found in the caterpillar state, and the third was reared from an egg obtained with others of the same kind in Norfolk. THE ALDER KITTEN (_Cerura bicuspis_). This moth (Plate 22, Fig. 3) differs from either of the two next following in being whiter, and in having both margins of the central band of the fore wings angled or bent inwards above the middle; this is markedly so on the outer side. The band itself is black, inclining to purplish rather than grey. Barrett mentions a specimen without central band or cloud towards tip. [Illustration: FIG. 19. COCOON OF THE ALDER KITTEN.] According to Buckler, the caterpillar is yellow-green; head dark reddish-brown; at the back of the head commences a broad, reddish-brown blotch, which runs to a point on the back of the third segment, where is a slight elevation; on the fourth it recommences and becomes broader on each segment to the eighth, where it extends below and encloses the spiracles, thence it narrows to the tenth, continuing on the eleventh and twelfth as a broad stripe, and {59} widening on the thirteenth, where it again narrows to the tentacles; in the broad portion of this dorsal marking are faint indications of two or three orange spots; on each side it is broadly edged with pale yellow, and on the sixth, seventh, and eighth segments its margin is deeply indented. It feeds on alder and birch in July and August. The cocoon is shown in its natural position on birch bark (Fig. 19). This was kindly lent to me for figuring by Mr. L. W. Newman, of Bexley, who also had another in which lichen as well as fragments of bark were worked into the surface, so that the cocoon was less in evidence than the one portrayed. The moth emerges in May and June.