ECONOMIC IMPORTANCE OF INSECTS 569 



Cabbage butterfly. — Larva eats leaves of cabbages and may be destroyed by a spray 



of arsenate of lead or Paris green. 

 Hawk moths. — Larva feeds on leaves of grape and tomato vines. Spray. 

 Rose beetles. — Adults feed on leaves and blossoms of the rose. Spray with a soap 



solution. 

 Codling moth. — Larva injures apples and pears. Spray with arsenate of lead at 



the time petals fall. 

 San Jose scale. — Adults suck juices from the leaves and young twigs of fruit trees. 



Killed by ladybird beetles and by fumigation. 

 Aphids. — Adult females suck juice from leaves and young twigs. Spray with 



nicotine sulphate. 

 Boll worm or corn worm. — Larva lives in the ears of corn. 

 European corn borer. — Feeds on stalks, roots, and ears of corn plant. Controlled 



by burning cornstalks in the fall. 



Forest and Shade Tree Pests 



Tussock moth. — Larva eats leaves of shade and fruit trees. Destroy egg masses 



and spray in early spring. 

 Gypsy moth. — Damage and extermination the same as for tussock moth. 

 Forest tent caterpillar. — Larva eats leaves of shade and fruit trees. Destroy nests 



and spray. 



Self-Testing Exercise 



Mark in your workbook the correct statements : 



T. F. 1 . The cotton-boll weevil has done so much harm in the South 

 that that region will never recover economically. 



T. F. 2. The tussock moth destroys annually many corn fields. 



T. F. 3. Nature usually has a natural check on destructive insects, 

 as in the case of the ladybird beetle and San Jose scale. 



T. F. 4. Larvae which feed upon crops may be killed by fumigation. 



Review Summary 



Test your knowledge of the unit by: (1) rechecking on the survey ques- 

 tions ; (2) performing all assigned exercises ; (3) checking with your teacher 

 the scores of the various tests and trying again those that you missed ; (4) mak- 

 ing an outline of the unit for your notebook. 



Tests on Fundamental Concepts 



In a vertical column under the heading CORRECT write numbers of all statements you 

 believe are true. In another column under INCORRECT write numbers of untrue statements. 

 Your score equals right answers X 2|. 



I. Plant foods (1) come from grain, vegetables, sugar cane, and 

 orchards ; (2) are valued roughly in the following order : grains, 

 vegetables, orchard fruits, and citrus fruits ; (3) are valued at more 

 than animal foods ; (4) may come from all parts of a plant 



