A Guide for the Study of Animals Part 4

4. If any of the legs differ from the others or are of peculiar shape or length, describe them and tell what you think they may be fitted to do.

5. As a rule, beetles have harder "sh.e.l.ls" than other insects. Does this sh.e.l.l completely inclose the body, or can you find any soft parts exposed? How are the head, thorax, and abdomen joined so as to carry out the apparent purpose of protection? What is the outline of the body--a continuous line or one with many irregularities?

6. If possible, try to lift up one side of the "sh.e.l.l" from the hinder end of the body. You will discover that this portion of the sh.e.l.l is a pair of hard sheath wings, and beneath them is another pair. How are the under ones unlike the upper in size and texture? in use? in arrangement when not in use?

7. Does a beetle spend most of its life on the wing, like bees and flies? How might the body covering and the structure of the outer wings affect or determine the beetle's habits, even against its will?

8. Are the feelers or are the eyes of your specimen more easily distinguished? Upon which of the special senses does it seem to place most dependence?

9. Is your kind of beetle good for anything, either in nature or in human affairs? Make a statement regarding what good or what harm it may do.

THE DAMSEL FLY LARVA

_Materials._

Living larvae of the damsel fly in shallow watch gla.s.ses of water for individual use, and others in large pans or aquaria. Simple lenses or dissecting microscopes.

_Observations._

1. What is the color and the shape of the larva? how long is it?

Notice in what surroundings in the water the larva lives, and answer to yourself how its form and color would protect it in those surroundings.

2. Since the larva is an insect, though immature, its body is composed of three regions: head, thorax, and abdomen. How do these regions differ from each other?

3. What structures has your specimen to enable it to move from place to place? If fully developed wings are not present, what indication is there of their being formed?

4. What sense organs has the larva? Which ones seem to be the largest and most useful?

5. Although the aquatic larva is preparing for adult life in the air, there should be some arrangement for securing air in the water. Where do you find outgrowths of the skin which might increase the air-absorbing surface? How many of these structures are there? Look within them for the air tubes,--fine branching black lines.

6. If possible, without injury to the specimen, examine the larva's mouth. Try to discover how it is used and how it is protected when not in use.

_Suggested drawings._

a. The entire larva, 4.

b. A gill, as seen through the microscope.

c. The feeding apparatus, 10.

PLANT LICE AND SCALE BUGS

Plant Lice (Aphids)

_Materials._

Plant lice on various kinds of plants, such as house plants, golden glow, and other plants from the garden or field. Garden asters with root lice (the asters should be transplanted into pots).

_Observations._

1. Describe the size, appearance, and colors of the plant lice in your collection and their relation to the host plant.

2. Are the lice active or sluggish? (Compare with a house fly, for instance.) What proportion of them have wings? What is the usual method of locomotion?

3. Examining a single winged specimen, how many wings do you find?

How do they fold? What is the character of the wings?

4. What is the food of the plant lice? How is the food obtained?

(With a hand lens identify the piercing organ.) On what parts of the plants are they found? Does the plant show any indication of being harmed by the lice? If so, how?

5. Make a count of the plant lice upon a portion of a plant and estimate the whole number upon a plant. Why are plant lice a very serious pest?

6. If any plant lice have ants a.s.sociated with them, study the behavior of the ants in this curious relationship. What advantages result from this relationship of ant and aphis to either or both insects?

Scale Bugs

_Materials._

Twigs of trees, leaves, fruit, ferns, etc., infested with these bugs.

If possible, have samples of San Jose scales, maple scales, and oyster scales.

_Observations._

1. What is the general size and appearance of the various scale bugs in your collection? How do they differ in form and size and color?

2. Remove a scale and study it carefully with a lens. What is under the scale? Of what is the scale composed? What do you discover about these bugs to indicate that they are really insects?

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?

_Drawings suggested._

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.