7. What do you know about a caterpillar's appetite? How might caterpillars be beneficial or harmful? What means has nature of holding their numbers in check? 8. Recalling that caterpillars finally "sleep" for several days or weeks and awaken as winged creatures, how can you account for their appetites? THE TUSSOCK MOTH _Materials._ Directions for the study of the caterpillar stage will be found in the exercise "The Living Caterpillar," 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._ a. A caterpillar, × 2. b. A cocoon with its egg mass.