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MISC. PUBLICATION 318, U. S. DEPT. OF AGRICULTURE 



Figure 40. — Cicada. 



Cicadas or "locusts/' — Almost every autumn one hears shrill noises 

 in the trees. The maker of these shrill noises is called the dog-day 

 cicada or harvest fly. There are other similar insects, however, that 

 appear earlier in the season. Dog-day harvest flies have piercing 

 __ mouth parts and can suck the juices from 

 plants. The adults are about 1% inches in 

 length and have four clear wings that fold 

 shedlike over the back. They have incom- 

 plete changes in the life cycle. Some of these 

 species require 4 years to round out their life 

 cycle; others require a longer period. In 

 fact, one species of cicada requires 17 years. 

 The name "locust" is often applied to these 

 Homoptera, but incorrectly. The principal 

 injury is caused by the adult, which punctures the twigs of trees in 

 order to deposit its eggs inside. This injury is especially noticeable 

 when great swarms of the 17-year cicadas appear. The insect shown 

 here is the periodic cicada (Magicicada septendecim) . 



Leafhoppers. — Quite often annual plants begin to show signs of 

 stunted growth from no apparent cause, but when disturbed, tiny 

 insects can be seen flying from the plants. These insects, often in- 

 correctly called white flies, are really leafhoppers. The tiny beak 

 through which they suck plant juices causes a mot- 

 tled or stippled effect on the leaves of grapes and 

 many hardy plants. Some kinds of leafhoppers also 

 carry plant diseases from one plant to another. 

 Leafhoppers vary considerably in size and color, but 

 all are long and narrow with four wings, also rather 

 long and narrow, folded over the back when at rest. 

 Leafhoppers have incomplete life changes. The 

 nymphs are difficult to see because they are very ac- 

 tive and usually, when the plant on which they are 

 feeding is disturbed, scurry to the opposite side of 

 the leaf, away from the observer. The observer, 

 when fortunate enough to see a nymph crawling, will 

 note that it usually does not run straight forward 

 but somewhat sidewise. Leafhoppers feed on a wide 

 variety of plants. In the South they^ are active throughout the season. 

 In the Northern States some overwinter as adults and some as eggs. 

 The insect pictured here, the potato leafhopper 

 (Empoasca fahae), is approximately one-eighth of 

 an inch long. It may be controlled by spraying 

 with bordeaux mixture or pyrethrum, or by dusting 

 with sulphur. 



Mealybugs. — Anyone who has attempted to grow 

 house plants, especially coleus, has become familiar 

 with a downy growth which occurs along the main 

 stem, but too few people realize that this down 

 covers an insect, the mealybug. Mealybugs vary 

 considerably in size and structure and feed on a 

 wide variety of host plants. Although very tiny, 

 the insects are able to insert their sucking beaks 

 into the tender j>arts of the leaves and stems of plants. They are 

 practically all wingless, and both adults and young are obliged to 



Figure 41. — Leaf- 

 hopper. , 



Figure 42. — Mealy- 

 bug. 



