"I wonder," said Dick, "if birds take any pleasure in the prettiness of their eggs. If so (and I don't see why they shouldn't), there is a reason why birds which build in bushes and branches of trees should have pretty coloured eggs, as they have, and why birds which build in dark holes should have white or light-coloured eggs, otherwise they would not see them at all."
"That is a very ingenious theory, Dick, and it may have something of truth in it," answered Frank.
That night was a still, warm night, and the moths were out in abundance. As soon as it became dark they all went out with a dark lantern to hunt them, and they were very successful. As they were returning home they passed by an old wall covered with huge masses of ivy. Dick going close to it said,
"Do look here. There are hundreds of tiny sparkles. What can they be? Why, they are the eyes of moths. The ivy is covered with the moths, feeding on the flowers. Look how their eyes gleam." And truly it was a marvellous sight. When they turned the light of their lantern on them they saw that the moths were busy with a curious silent activity, flying from flower to flower, sipping their sweets.
"There are so many that I hardly know how to set about catching them," said Dick. "Many of these must be rare and many common."
"Sweep the face of the ivy all over with your net as rapidly as you can, and keep them in your net until we get home, and then we can kill and pick out all that you want," counselled Frank.
Dick followed his advice, and with a dozen rapid sweeps of his net he seemed to have filled it. Closing the net by turning the gauze over the ring, they walked quickly back to the boat-house, and carefully closing the door and window, they opened the net and let them all out into the room, and then caught them singly. In a couple of hours they found that they had secured about fifty specimens, comprising twenty different species.
During the summer a strange creature which fed on the potato plants had much frightened the country people, who thought it a sign of a coming plague. It was a large caterpillar, of a lemon-yellow colour, with seven slanting violet stripes on each side and a horn on its tail. The people in the neighbourhood of Hickling, knowing that Frank and his companions were fond of collecting such things, brought some to them, and by this means they became possessed of more than thirty specimens. They were the larvæ of the death's-head moth, the largest of all our British moths. It is remarkable not only for its size, but for two other things, each of which is very curious. On its thorax it has a perfect delineation in white of a skull, or death's head, with a pair of cross-bones below it. In addition to this singular mark, it—and it alone of all our moths and butterflies—has the power of making a squeaking noise, which it does when it is touched or annoyed. How it makes this noise no one seems to know. At least there are so many conflicting opinions that the matter may be said to be still in doubt.
The boys fed the larvæ on potato-leaves put in a box in which there was placed about six inches of earth. When the larvæ had finished their eating, they dived into this earth and turned into the pupæ state. In the autumn the perfect moths came out, but only about half of the number reached the final stage. The others died in the pupæ state. However, Dick had plenty of specimens for his cabinet and for exchange.