EXERCISES ON CHAPTER XIX. 1. Examine the following animals, and find out (a) which are arthropods, (b) which are insects: tortoise, spider, grasshopper, lobster, earwig, centipede. Give reasons for your conclusions. 2. Keep a grasshopper under a tumbler with a small sod of grass. Observe its habits, and find out how it “chirps.” Compare its structure with that of the cockroach. 3. Compare a cockchafer with a water-beetle. In what order of insects would you place the cockchafer, and why? 4. Compare other water-beetles with Dytiscus, and try to trace their life-history. 5. Observe the habits and examine the structure of the water-boatman. What reasons can you find for excluding it from the beetle-order? 6. Examine a daddy-long-legs, and try to find the two stumps which are all that remain of the hind-wings. 7. Look for “blood worms” (larvae of the harlequin fly) in horse-troughs and sluggish streams in summer; keep them in a saucer of water with a few dead leaves. Observe their habits and describe the appearance of the pupa. What kind of insect emerges from the pupa? 8. Keep caddis-worms in an aquarium and describe their habits. 9. Examine the leaves of stinging nettles for caterpillars in June, and try to rear butterflies from them. Carefully notice from which kind of caterpillar each butterfly is derived. 10. Look for caterpillars of the Privet Hawk Moth on privets and lilacs on August and September evenings. Keep some, with earth and twigs of the food plant, in a covered flower-pot, and observe their method of pupation. 11. Compare the colouration of the wings of butterflies and moths with that of the plants they most frequent, and describe any cases of protective colouration which you find. [Pg 372] CHAPTER XX. SOME CRUSTACEANS, MOLLUSCS, AND WORMS. 65. SOME COMMON CRUSTACEANS. 1. The crayfish and lobster.—(a) Habits.—Readers in limestone districts will probably be able to find crayfishes in the streams, and the habits of the animals in their natural surroundings should be observed and described. Other readers will be able to obtain live specimens from dealers.[35]