18 MISC. PUBLICATION 318, U. S. DEPT. OF AGRICULTURE 
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 114 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. 
FicurE 40.—Cicada. 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 periodical cicada (A/agicicada 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. 
Leathoppers 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 Ficurz 41—Leaf- 
but somewhat sidewise. Leafhoppers feed on a wide one 
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 
(E’mpoasca fabae), is approximately one-eighth of 
an inch long. It may be controlled by spraying 
with DDT, bordeaux mixture, or pyrethrum, or by 
dusting with sulfur. 
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 
Biguny 42. Mealy- wide variety of host plants. Although very tiny, 
the insects are able to insert their sucking beaks 
into the tender parts of the leaves and stems of plants. They are 
practically all wingless, and both adults and young are obliged to 
