The eggs are laid in April on the twigs of the birch (_Betula alba_), and the young caterpillar emerges early in May. It is gregarious at first, but loses its social tendencies as it gets older. When full grown, it is of a pale green colour, with white spiracles, a dark green line down the back, and an oblique white stripe on each side of each segment. The sides are dotted with black and brown, and there is a conspicuous hump on the top of the twelfth segment. When fully grown it spins a cocoon among the dead leaves beneath the tree, and in this it spends the winter months in the chrysalis state. Family--SATURNIIDAE _The Emperor Moth_ (_Saturnia pavonia_) Here is another family with but one British member; but in this, as in the last case, the only representative is a really beautiful insect. The male _Pavonia_ is shown on Plate X (fig. 8), and will need no written description as an aid to its identification. The female is larger, and similarly marked, but the ground colour of the wings is pale grey. This moth is abundant almost everywhere, and may be looked for in the neighbourhood of heaths and woods early in the month of May. The larva feeds on a large number of plants and trees, among which may be mentioned the willow (_Salix alba_), blackthorn (_Prunus spinosa_), elder (_Sambucus nigra_), whitethorn (_Crataegus oxyacantha_), bramble (_Rubus fruticosus_), heaths (_Erica tetralix_ and _E. cinerea_), and the meadow-sweet (_Spiraea ulmaria_). Its colour is a lovely green; and each segment has several pink tubercles, each surrounded by a black ring, and giving rise to a tuft of short black hairs. The spiracles are orange. In the autumn it spins a pear-shaped cocoon of silk, open at the small end (fig. 28). It may here be mentioned in passing that, in the case of some of the larger moths of the few preceding families, the young entomologist is likely to meet with larvae more frequently than the perfect insect. These moths, however, are mostly very hardy and easily reared; and a beginner cannot do better than endeavour to obtain either ova or larvae, in order that he may be able to watch the different species through their various stages. Family--DREPANULIDAE We now reach a family containing six small moths that differ in many important particulars from those we have just been considering. They are of such slender build that a beginner may easily mistake them for Geometers. Their wings, though small, are broad, and well proportioned to their bodies. In five cases out of the six the front wings are more or less hooked at the tips, and on this account the moths in question are called the Hook Tips.