300 



ELEMENTARY ENTOMOLOGY 



Exercise 51. Observations on tJie structure of the nymphs. Write up a 

 careful description of the nymphs, noting the details of structure. In the 

 description, refer to and use the terms with which you have already become 

 familiar in your description of other forms. 



Exercise 52. Habits of the nymphs. Make as many notes as possible on 

 the general habits of the nymphs, noting their methods of feeding, locomotion, 

 secreting themselves, etc. (see page 98). 



Exercise 53. Observations on the transformation of nymphs. Note care- 

 fully whether or not the nymph molts, or sheds its skin, and, if observed, how 

 the act is performed. Toward spring the nymphs should be placed in the sun- 

 light as much as possible. Each dish should also be provided with a number 

 of sticks, up which the nymphs may crawl when they are ready to transform to 

 the adult stage. If possible, observe this transformation and write up a com- 

 plete set of notes on the subject. 



SECTION XIX. COMPLETE METAMORPHOSIS. LIFE HISTORY OF 

 THE CABBAGE BUTTERFLY (PONTIA RAPAE) 



Material. The following instructions have been prepared especially for the 

 study of the cabbage butterfly, though the life history of any of the other Lepi- 

 doptera may be studied in the same manner, substituting, of course, the proper 

 food plants. Each student should be provided with a flowerpot in which is grow- 

 ing a young cabbage plant. If this work may be begun by the middle of Septem- 

 ber, cabbage butterflies should be collected and one pair placed in each of a 

 number of breeding cages (see Chapter XXIII). The pots containing the young 

 plants can be placed in the cages, and daily observations made for the presence 

 of eggs. After the eggs hatch, a large lantern globe, the top of which has been 

 covered with cheesecloth, should be placed over each plant, to prevent the 

 escape of the larvae. 



Exercise 54. Egg deposition. The student should, if possible, determine 

 and make notes of the following points : 



1 . On what part of the leaf are the eggs deposited ? 



2. Are they deposited in clusters or singly? 



3. The number of eggs deposited by one female. 



4. The period of incubation. 



5. Describe and make drawings of the eggs. 



Exercise 55. Observations on the larva. Determine and make notes of the 

 number of molts, describing each of the larval stages. 



Exercise 56. Observations on the pupa. If possible, observe the transfor- 

 mation of the larvae to the pupal form. Note the locality selected for pupation, 

 the attachment of the pupa, and length of time in the pupal stage. Also draw 

 and describe. (After pupation the pupae should be removed to a cool, dark 

 place and left until spring, or, if wanted for more immediate use, they should 

 be placed in a light, warm room, where they will probably emerge in a short 



