A Guide for the Study of Animals. Worrallo Whitney
and directions for the study of the adult male form will be found in the exercise "The Living Butterfly or Moth." The female tussock moth is a wingless, thick-bodied creature, gray in color, very downy, and about three fourths of an inch long. The following directions apply more particularly to the study of the cocoons and the general harmfulness of the tussock moth.
This exercise may be done best outside of the classroom, the pupil answering the questions on scrap paper and rewriting these notes in the laboratory. Living caterpillars, cocoons, some of them bearing their frothy masses of wax and eggs, pupæ, and adult moths of both sexes may be used in the laboratory.
Observations and Questions.
1 On what kinds of trees are the cocoons and the caterpillars generally found? What effect have the caterpillars on the trees, and what may possibly be the final effect upon the trees of the locality or the entire district?
2 Upon what part of the tree are the cocoons made, and why? Where on the bark are they, and why?
3 Is the opening of the cocoon at the upper or the lower end? What reason can you assign for this?
4 Count the number of cocoons upon the entire tree or estimate it by counting those upon a part of the tree. Now count the number of eggs on a cocoon. Assuming that one half of the cocoons bear eggs, calculate the number of caterpillars on a tree next year.
5 How is the waxy covering of the eggs a particularly good protection against winter weather?
6 Investigate the interiors of several cocoons and state what you find.
7 On the pupa find the jointed and tapering hinder end, abdomen, and at the head region and lying along the under side, the marks of the legs and the feelers, and possibly the wings, all pressed close against the body. Find also the breathing pores along the sides of the abdomen.
8 Unlikeness between male and female is called "sexual dimorphism." Explain how the tussock moth shows this. For what work does each form seem particularly adapted?
9 What methods would you use that the tussock moth might be destroyed or kept out of a community?
The numerous small worm-like creatures often found are the caterpillar stages of another insect, an ichneumon fly, which laid its eggs under the skin of the tussock caterpillar. How has their development affected that of the tussock moth? What great result does nature accomplish by this arrangement?
Suggested drawings.
1 A caterpillar, × 2.
2 A cocoon with its egg mass.
3 A pupa as seen from the under side.
4 An adult moth, either male or female.
THE LIVING BEETLE
Materials.
Living beetles in cages, together with portions of the plant upon which they are found; or if water beetles are used, they should be kept in aquaria. Individual specimens in battery jars or wide-mouth bottles, and preserved beetles in pans or vials for reference.
Observations.
1 Upon what plant or in what surroundings is your kind of beetle generally found? If you can, give its common name.
2 What is the length, breadth, and thickness of your beetle? Would you describe it as a "small" insect or a "large" one?
3 Of what general color is it? Describe any color markings you see.
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 "shells" than other insects. Does this shell 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 "shell" from the hinder end of the body. You will discover that this portion of the shell 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 larvæ of the damsel fly in shallow watch glasses 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.
1 The entire larva, × 4.
2 A gill, as seen through the microscope.
3 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