ing one or more rows of small spines extending the length of the 
hind tibiae. Because of the nature of their feeding, which con- 
sists of piercing plant tissues with their mouth parts and 
sucking the juices, the damage they cause is usually not recog- 
nized or is attributed to other factors. About the only visible 
effects of leafhopper feeding are the white stippling of foliage or 
the browning, withering, and curling of leaves. Because of the 
difhculty in observing or evaluating the damage to trees, very 
little is known of its magnitude or importance. The probability is 
that it is grossly underestimated. These insects, in fact, may con- 
tribute significantly to the general unproductiveness of many 
stands of valuable hardwoods in Eastern United States. Many 
species are also vectors of destructive plant diseases, especially 
diseases of virus origin. 
Some species of leafhoppers spend the winter in the egg stage; 
others as adults. Overwintering eggs usually hatch in May or 
June, and the young nymphs feed on new, tender leaves. Over- 
wintering adults emerge during the first warm days in spring and 
lay eggs as soon as the leaves of their hosts are fully developed. 
These eggs hatch in about 10 days. As a rule there are one or two 
generations per year; sometimes, more. 
Forest and shade trees serve as hosts for many species of 
Hrythroneura, Empoasca, and Typhlocyba (189). Several species 
of Idiocerus feed on willow and poplars. Various species of Mac- 
ropsts feed on poplars, willow, and honeylocust. Certain species of 
Scaphoideus, Gyponana, and Ponana oecur on American elm; oaks 
are infested by species of Alebra, EHutettix, and Penthimia. This is 
only a partial listing of genera and species known to attack trees; 
the total number is far greater. 
The most important leafhopper as far as forest and shade trees 
are concerned is the white-banded elm leafhopper, Scaphoideus 
luteolus Van D., the vector of elm phloem necrosis, a virus disease 
of American elm (21). Adults are difficult to separate from those 
of closely related species, but not so the nymphs (fig. 14). After 
the second instar, practically all of the nymphs are dark brown 
with a transverse white band across the dorsum. This band lies 
just behind the thorax and covers the first two and part of the 
third abdominal segments. The species is widely distributed in 
Eastern United States, from New York west to Kansas, Nebraska, 
and Iowa, and south to Georgia and Alabama. 
The white-banded elm leafhopper lays its eggs in the cork par- 
enchyma of elm bark. When the eggs hatch the young nymphs 
wander in search of leaves on which to feed. The first of these to 
be found usually are on tiny branchlets growing from the trunk. 
A dozen or more young nymphs may be found clustered on the 
undersurface of one of these leaves, where they feed on the mid- 
ribs or larger veins. Excessive feeding often causes the apical 
portions of the leaves to turn brown and die. Older nymphs are 
more widely distributed throughout the crown of the tree (22). 
Elm phloem necrosis virus is transmitted by the adults which 
feed first on the leaves of diseased trees and then on the leaves of 
healthy trees. Studies have shown that a period of several days 
must elapse after the insect feeds on a diseased tree before it can 
transmit the virus. All of the details of the life cycle of the species 
69 
