12 A GUIDE FOR THE STUDY OF ANIMALS 



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 caterpil- 

 lars, cocoons, some of them bearing their frothy masses of 

 wax and eggs, pupae, 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 cater- 

 pillars 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 t 



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 



The numerous small worm-like creatures often found are the cater- 

 pillar stages of another insect, an ichneumon fly, which laid its eggs 

 under the skin of the tussock caterpillar. How has their development 

 aflFected that of the tussock moth ? What great result does nature ■ 

 accomplish by this arrangement ? 



