PROBLEM 3. Honj) We Try to Solve Our Insect Froblems 



395 



Fig. 344 One iicst of tent caterpillars may eat 

 all the leaves from a small tree. The caterpillars 

 return to their vest at night. At that tinie they 

 can be destroyed by bnrning the nest, (general 



BIOLOGICAL SUPPLY HOUSE) 



plies with such rapidity that in some 

 years it causes losses in the grain fields of 

 the Mississippi and Missouri valleys that 

 amount to millions of dollars. The eggs 

 are laid in the ground or on the young 

 stems of grains or wild grasses. After 

 five or six weeks the bugs are full-grown 

 and by this time their feeding ground is 

 pretty well exhausted. Then they migrate 

 in vast hordes. Though they have wings 

 they march on foot to a neighboring 

 field. They move forward blindly so that 

 millions can often be trapped in ditches 

 filled with kerosene. This is only one of 

 several ways in w^hich the farmer fights 

 this destructive insect. Can you think of 

 some other possible ways? 



The gypsy moth, which is common in 

 the eastern states from Maine to New 

 Jersey, strips and, in time, may kill trees. 

 The larvae (caterpillars) eat leaves of al- 

 most any kind, even the needles of ever- 

 greens. The eggs which are laid during 

 the summer in large masses near the 

 ground hatch early the following spring. 



Figure 343 is a photograph of the dark, 

 hairy, little caterpillars moving up a tree 

 trunk. One of the best ways to protect 

 individual trees is to circle the trunk 

 with a band of sticky material which 

 traps the caterpillar. 



Destroying insects with stomach poi- 

 sons. Poisons of various kinds, frequently 

 arsenic compounds such as Paris green, 

 are sprayed on plants. Other poisonous 

 compounds are dusted on. Sometimes 

 this is done on a large scale by using air- 

 planes. By these means we can kill in- 

 sects with biting mouth parts which feed 

 on the exposed parts of plants. 



Stomach poisons can be used success- 

 fully against the larva of the cabbage 

 butterfly. This is a small white butterfly 

 common around gardens where it sucks 

 nectar. It lays eggs on the cabbage and 

 related plants. The larvae with strong 

 biting jaws may be found two weeks 

 later. The inch-long bluish-green larvae 

 match the plant so exactly that they are 

 scarcely visible. This insect came to us 

 from Canada. Within eight years it 

 reached the Gulf of Mexico, damaging 

 cabbage patches along its route. We 

 failed to stop its spread partly because, 

 like many insects, the cabbage butterfly 

 multiplies very rapidly, having three 

 broods in a season, and partly because 

 few farmers took pains to spray their 

 plants. They allowed the insects to mul- 

 tiply and spread to their neighbors' 

 crops. 



Another insect we fight by spraying a 

 stomach poison is the codling moth. It 

 attacks apples and pears in its larval stage, 

 costing New York State farmers alone 

 some 3 million dollars every year. The 

 small adult moth matches the color of 



