478 



THE ANIMALS OF THE EARTH 



the body, namely, head, thorax, and abdomen ; on the head of 

 each are eyes, mouth, and jointed feelers; on the thorax are 

 three pairs of jointed legs; and the abdomen of each is made 

 up of distinct rings or segments. Can you find all of these 

 parts on a grasshopper ? on a butterfly ? 



Insects and mollusks are invertebrates, that is, animals with- 

 out a vertebral column or backbone. 



Helpful insects. Many insects are helpful to man : the 

 silk moth larva furnishes silk ; the bee, honey ; a scale insect in 

 Mexico, cochineal, a red coloring matter; a Chinese insect 

 secretes wax, and an India insect is responsible for lac, a sub- 

 stance from which varnish is made. But the most valuable in- 

 sects are those which, like bees and wasps, visit flowers for nectar, 

 and in so doing transfer pollen from flower to flower and assist 

 in the formation of fruit and seed. 



How birds help the farmer. Most song birds live upon 

 insects that destroy crops. Flycatchers take their living from 

 the insects that swarm in the air. Vireos live upon measure 

 worms and similar morsels. A flock of birds may detect a 



small body of locusts early in 

 the season, and devour them be- 

 fore they find opportunity to 

 lay their eggs. Thus a great 

 disaster to the corn crop may be 

 averted, for when the breeding 

 of the locusts goes on unchecked, 

 they sometimes descend in vast 

 clouds and feed upon growing 

 corn, grass, wheat, and trees, and 

 in a few hours destroy every 

 green thing in sight over an area 

 of many square miles. Such a loss of food materials means 

 higher prices to the consumer. 



FIG. 346. Robin's nest. 



