You can easily tell the female of this butterfly from the male, for her front wings have a broad black border, while that on the wings of her mate is very narrow indeed. The caterpillar is greenish-yellow in colour, with a black head and black legs, and a bright green streak running along the middle of the back. When it has reached its full size it turns into a small yellowish-brown chrysalis. PLATE XII THE BRIMSTONE BUTTERFLY (2) This very handsome insect is common in almost all parts of the country, and is one of the very first butterflies to be seen in the spring. On warm, sunny days in March, or even in February, you may often meet with it. For it is one of those butterflies which “hibernate”--that is, it comes out of the chrysalis in the summer or early autumn, and then sleeps all through the winter in some snug retreat, from which it is always ready to come out for an hour or two when the weather is a little warmer and finer than usual. The male Brimstone is a good deal handsomer than the female, for his wings are of a bright daffodil colour, while those of his mate are pale greenish-yellow. The caterpillar feeds on the young leaves of buckthorn bushes, and is dull green in colour, sprinkled all over with tiny black spots, from each of which sprouts a slender white bristle, and the chrysalis, which is fastened by a silken belt round its body to a twig of the food-plant, is bright apple-green marked with yellow and purple-brown. [Illustration: PLATE XIII 1. Clouded Yellow 2. Pale Clouded] PLATE XIII THE CLOUDED YELLOW (1) I wonder if you have ever seen this very handsome butterfly alive. Very likely you have not, for although just now and then it is very common indeed, it nearly always becomes quite scarce for several years afterwards, and you may look for it summer after summer without seeing it at all. It makes its appearance in August and September, and the best places in which to look for it are clover and lucerne fields near the seaside. But it is also very fond of flying about on railway banks; and if you try to chase it _there_ you will find that you will have to run very hard indeed if you want to catch it! In fact, one butterfly collector used to say that it was of no use trying to do so unless one wore a pair of seven-leagued boots! The caterpillar of the Clouded Yellow butterfly is of a bright grass-green colour, with a white line on each side, marked with yellow and orange. It feeds on the leaves of lucerne, trefoils, and clover in June and July, and then changes into a green chrysalis shaped something like that of a “large white,” with a pale yellow stripe on each side, and a number of black and reddish-brown spots. PLATE XIII THE PALE CLOUDED YELLOW (2)