168 OTHER INSECTS 



rious forms can be brought to the laboratory for individual study or 

 demonstration. Observe their way of moving and their voracious 

 habits in feeding. How do the structure and use of the mouthparts 

 differ in the larva and adult? The caterpillars of moths will often 

 spin their cocoons in the cages where they are kept, or such cocoons 

 may be collected and given out for study. Cut one open and find the 

 pupa, or resting stage, within. Notice the silk of which the cocoon 

 is composed. Such cocoons, or those collected during the late fall, if 

 uninjured, may be kept in cages, and the emergence of the adult insect 

 observed at some subsequent time. Cocoons are characteristic for 

 the moths. The larvse of butterflies typically have a naked pupa, 

 called a chrysalis (Fig. 72 j), which is protected by a tough skeleton 

 from which the adult insect emerges at the final molt. Understand 

 the complete life-history in each of the orders studied and be able to 

 explain the difference between the type of life-cycle in butterflies and 

 moths and that found in insects such as the grasshopper. Examine 

 carefully all the details of Figs. 72 and 73. 



Exercise 4. — Other Orders. 



(i) Of the remaining orders of the insects, three are more com- 

 monly known and recognized by popular names. These are the Hem- 

 iptera, or true bugs; the Diptera, or two-winged flies, of which the 

 house-fly is our most common representative; and the Odonata, or 

 dragon-flies. Observe as many representatives of the different orders 

 as are available, noting structural features such as mouthparts, wings, 

 and markings, which serve as taxonomic features. 



