Of course you know this pretty insect very well indeed by sight, for it is one of the commonest of all our British moths. You cannot possibly mistake it for any other, because of its snowy white wings and the thick tuft of long yellow hairs at the end of its body, from which it gets its name of “Gold-tail.” In the female moth this tuft is very long and thick indeed, and she puts it to a most curious purpose. For when she has laid her eggs she strips off the golden down from her tail and covers them carefully over with it, leaving the tip of her body almost bare!
The caterpillars which hatch out of the eggs are most beautiful little creatures. They are black in colour, with three rows of tiny pimples, so to speak, on each side, from every one of which springs a little tuft of hairs. Those of the upper row are jetty-black; those of the middle row are white; and those of the lower one are bright scarlet. Besides this, there are two scarlet stripes running down the back, and just behind the head is a sort of hump, which is bright scarlet also.
You may find these handsome caterpillars on the leaves of hawthorn, and also on those of plum trees. When they are fully fed they spin a silken web among the leaves, and turn to chrysalids, out of which the moths hatch in July.
You may sometimes see this handsome moth resting on a fence in May, and “drying” its wings after coming out from the chrysalis. The female is not quite like the male, for she is generally a good deal larger, with a very much stouter body, and instead of having a dark brown stripe across the middle of her wings, as he has, she has two wavy lines, one rather before the middle, and the other rather beyond it.
The caterpillar of this moth is generally known as the “hop dog”; but I cannot tell you the reason why, for it feeds a great deal more often on the leaves of oak, lime, and hazel than it does on those of the hop. It is one of the loveliest of all our British caterpillars—very hairy, and of the most delicate pale green colour, with three bands of deep velvety-black round its body. On its back are four brush-like tufts of long yellow hairs, pointing forwards, and on its tail is another still longer tuft of the same colour, which points backwards. When it is fully grown it spins a very slight silken web among the leaves, and turns to a hairy chrysalis. You may find it feeding in July and August.