17. Relate the life-history of the frog, from the time of hatching to the end of the first summer. (1897)
18. Give some account of the habits of a young tadpole a few days after hatching, especially with respect to locomotion and feeding. Make a drawing of such a tadpole in side view, three times the natural length. (1904)
19. Describe the hind leg of a frog, and explain the ways in which it is used. (1905)
20. Show how a full-grown frog is enabled to live either in air or in water. (1906)
CHAPTER XIX.
THE HABITS AND LIFE-HISTORIES
OF COMMON INSECTS.
62. THE COCKROACH: A TYPICAL INSECT.
1. Habits.—In what places have you seen cockroaches? Are they often to be seen during the day, or do they, in general, come forth only at night? What is the colour of the body? Put a live cockroach under a tumbler, and watch its movements. In what position is the head held? Notice the long feelers; how are they used? Look at the lower part of the head, and try to see the palps, which resemble small feelers. How many legs has the cockroach? Watch the rhythmical movement of the hinder part of the body. Soak a small piece of bread in milk or water, and put it under the tumbler; watch the cockroach feed. How does it use the palps? Notice that the jaws move from side to side. How does the insect clean itself?
2. External characters.—Put a cockroach into a test-tube, and dip the tube into boiling water; this kills the insect instantly. Notice the thin “shell” which covers the outside of the animal. Make out that the body consists of (a) head, carrying the eyes, feelers, and jaws; (b) thorax, carrying the wings and legs; and (c) abdomen. Examine them in turn.