“When the larvæ are full grown, they crawl out of the pond and bury themselves in ground. Here they pass the winter in the pupa stage. They come out in spring, fully-formed beetles, and pass the remainder of their lives in the water.” “What are these curious creatures that crawl among the water weeds?” Frank asked. “They are very like the ‘slaters’ which we find among old wood-work in the garden.” “That creature is the ‘water hog.’ Its proper name is _Asellus_, and it is very closely related to the garden ‘slater’ or wood-louse. “These water hogs, like the whelks, are very useful in an aquarium. They eat up all waste matter, and so help greatly to keep the water fresh. “By the by, I want you to watch the whelks from day to day. They usually lay their eggs in a clear, broad band on the inside of the glass tank; and with our lenses we can watch the changes in these eggs nicely.” Exercises on Lesson X. 1. Procure some “water boatmen” from the nearest pond (see Appendix), feed them upon flies, and watch their habits. Notice particularly their method of swimming and of feeding. 2. We should not keep all our pond animals in one tank. Can you explain (giving examples) why this is? 3. Write the life-history of the diving beetle. 4. Make large sketches of the diving beetle and its larva. Compare them. [Illustration] Water Beetles. Hog Lice. Water Whelks. Water Boatman. XI.—WASPS. The wasp’s nest was found at the edge of the wood, hanging from the branch of a small tree. It was greyish white in colour, shaped like a pear, and about the size of a hen’s egg. [Illustration] Queen Wasp. Worker Wasp. Queen Bee. Worker Bee. Uncle George removed it from the branch and carried it home carefully, for it was very light and very fragile. He took a pair of scissors and cut through the thin walls so as to remove nearly half of the coverings. When he had finished cutting, two thin, papery shells fell upon the table, one a size smaller than the other. “Examine the stuff the wasp’s nest is made of, and tell me what it is most like, boys,” he said. “It is more like paper than anything else,” said Tom. “It _is_ paper,” said his uncle. “Where did the wasps find this paper?” Frank asked. “Not ‘_wasps_,’ Frank, but _wasp_,” his uncle answered, “for this nest was all built by _one_ wasp. The insect did not find the paper. She made it. It was the wasp who first taught man to make paper. “The queen wasp awakens from her winter sleep in spring, and at once sets about making her nest. She gathers tiny fragments of wood and bark, chews them up, and mixes them with a fluid from her mouth. This, when it hardens, is paper. “First she makes a stiff rod, or pillar, of paper. This hangs down from the branch and forms the centre of the nest. Round this are built the walls of her house.