There were several in the tank. Uncle George lifted one out with a small gauze net. He placed it in a saucer of water and asked the boys to sketch it. “It has six legs,” said Frank. “Its head is large and flat, and there are two things like horns sticking out of it.” “These are the creature’s jaws,” said his uncle. Uncle George touched the creature’s head with the point of his pencil. Instantly the long, curved fangs moved apart, and the creature sprang at the pencil and closed its fangs upon the wood. [Illustration] 1. Larva of Diving Beetle. 2, 3. Head, showing how Fangs work. 4. Larva seizing Tadpole. “What a fierce creature,” said Tom. “Yes,” replied his uncle. “We must remove the others from the tank, or there will be nothing left alive in it. See, one of them has caught a tadpole already.” And, sure enough, the creature had sunk his cruel pincers deep into the body of a tadpole. He shook the tadpole as a dog would shake a rat. “Those huge fangs are hollow,” Uncle George continued. “With them he sucks every drop of blood from his victim’s body. In this way he devours tadpoles, whelks, little fishes, and even his own weaker brethren. “We shall have to put these larvæ in a tank by themselves, and feed them upon pieces of fresh raw meat, to keep them from devouring one another. “Now, boys, I am going to describe this larva. Look closely, and see if I am right. You can correct your drawings as we go along. “His body, which is nearly two inches long, is narrow at each end and broad at the middle. It is divided into twelve segments, and to each of the first three of these segments a pair of legs are attached. His large, flat head is almost heart-shaped. At its broad end are a pair of large, beady eyes, three pairs of organs which look like feelers, and the two large, curved fangs with which he seizes his prey. “Notice how beautifully the legs are adapted for swimming. They are edged with long, stiff hairs, which stand out flat with every down stroke, but fold in when the legs move upwards. That is how the creature is such a graceful swimmer. “The last three segments of his body are thickly covered with long hairs. His tail is divided into two long plumes. You can see what these are for, I hope.” “Oh yes,” said Frank. “Like the parent beetle, the larva comes often to the surface and hangs downwards with his tail exposed to the air. So these plumes must be his breathing organs.” “And do these long, slender creatures actually become broad, stout beetles like the one we returned to the pond to-day?” Tom asked. “Yes, Tom, they do. Just as your green caterpillar became a beautiful white butterfly. These larvæ hatched out of eggs which were laid by the female beetle in the stem of some water weed. She first cuts a slit in the water weed, and then places an egg in the slit.