572 Animal Biology 



[queen]). The workers may be modified as soldiers or as small or large 

 workers. Ants usually live in terrestrial tunnels, in hollow cavities in 

 wood and plants, or in mounds in the ground. The leaf-cutting ant 

 carries pieces of leaves into the nest where other workers make them 

 into balls in which they cultivate and regulate a growth of fungus (a 

 lower type of plant). In this way white masses of food are produced 

 and stored for the colony. The carpenter ant builds its nest in the dead 

 wood of trees and buildings, thus impairing their usefulness. The corn 

 louse ant carefully uses and protects a very detrimental plant Aphid 

 which attacks the roots of corn plants. In this way the Aphid is some- 

 what protected. The common red and black ants are common house- 

 hold pests which cause untold annoyance. They destroy large quanti- 

 ties of foods, grasses, and lawns. 



Fig. 306. — An adult ichneumon wasp of the order Hymenoptera. Note the 

 long ovipositor by means of which eggs are frequently laid in the larvae of other 

 insects and in which the eggs develop parasitically. 



The "gall flies" (Hymenoptera) possess long ovipositors by means of 

 which eggs are deposited in plant tissues. The plant is thus stimulated 

 to develop abnormal, enlarged growths known as galls (Fig. 271). The 

 gall naturally protects the young gall fly. The ichneumon wasps or 

 flies (Fig. 306) are parasitic Hymenoptera which attack many injurious 

 insects, such as tussock moths, cabbage butterflies, tent caterpillars, and 

 corn borers. 



PHYLUM 12— CHORDATA (LAMPREYS, SHARKS, FISHES, 

 FROGS, REPTILES, BIRDS, AND MAMMALS) 



This phylum of animals contains such a variety of types that it is 

 difficult to discuss the economic importance of its members without 

 taking each class by itself. The following examples of each class will 

 suffice to give a representative idea of the group as a whole. 



