3. What can be said about the number of scale bugs? Why are they difficult to exterminate? How can they be distributed from one place to another, as from orchard to orchard, since only the males have wings?
a. A single aphis as seen with hand lens.
b. Various scale bugs as seen with a hand lens.
c. Twigs showing the distribution and numbers of scale bugs.
Water bugs and beetles of several species in small aquaria covered with a wire net.
1. With what legs does the bug swim? Describe their appearance and tell how used and how fitted for this use. Which legs are not used in swimming?
2. Remove the bug from the water for a moment to test other methods of locomotion, as jumping, crawling, flying. What do you discover?
3. Watch the bug as it gets a fresh supply of air, and describe the process. Where is the air stored for use when under water? Does the bug sink or rise when it stops swimming? Why?
4. Identify the bug's mouth parts. What is their appearance and probable manner of use? How are the forelegs fitted for grasping food?
5. What is the shape of the body? What is the position of the wings? Do the two cover (fore) wings meet in a straight line or do they cross at their tips? Are they smooth throughout and sheath-like, or are they thick at the base and thin at the tips?
Summarize your study of the bug by enumerating the various ways the bug is adapted for life in the water.
Use the same questions for the study of water beetles as for water bugs. In addition answer the following:--
1. Identify the eyes of the whirligig beetle and note their peculiar construction. How can you explain this peculiar form of the eyes on the basis of use? Why are the antennæ of both water bugs and beetles so small?
a. The dorsal view of both bug and beetle.
b. Ventral view of the bug's head to show the beak and first pair of legs.
The books in a zoölogical library may be roughly divided into three groups:--
1. Reference books. a. Advanced textbooks. b. Elementary textbooks. c. Natural histories. d. Books for classifying or naming animals. 2. Descriptive books. e. Life histories and habits of animals. f. Adventures with animals--popular accounts of animals seen on walks and travels. 3. Economic zoölogy. g. Books on harmful animals and methods of destroying them. h. Books on useful nondomesticated animals and their products. i. Books on domestic animals. j. Books of a general nature not included in the above.