298 



ZOOLOGY 



they breed, with the ploughing up of the eggs and the destruction of the young, 

 there is reason to hope that these migrations are at an end. Accounts of similar 

 migrations of locusts are recorded in the history of the old world. These migra- 

 tions and their effects illustrate how climatic conditions in one locality may change 

 the balance of life in another. The second chapter of the prophet Joel gives a 

 vivid account of a visitation of locusts. See Fig. 139. 



FIG. 138. 



FIG. 138. Campodea, a Thysanuran. Magnified 30 times. By J. W. Folsom. 



Questions on the figure. In what respects does this form seem intermediate 

 between the Myriapods and the higher insects? How does this compare with the 

 larvae of insects which undergo a metamorphosis? Can you distinguish head, 

 thorax, and abdomen? 



Order Neuroptera (nerve-wings}. The members of this order have a more or 

 less complete metamorphosis. Usually there are two pairs of netted membranous 

 wings. The mouth parts are suited to biting. This group includes many diverse 

 forms which the entomologists distribute into nine or ten orders. These are: 

 the Ephemerida, or may flies whose adults may live for only a few hours, although 

 the larvae may require from one to three years to develop; the Odonata, or carnivo- 

 rous dragon-flies, and damsel-flies; the Plecoptera, or stone-flies; the Isoptera, or 

 termites (white ants) which are social, polymorphic forms; the Corrodentia, book- 



