mall leaf-hopper (_Typhlocyba comes_) infests
the grape in greater or less numbers, feeding on the lower surface of
the leaf. Grape-growers commonly call these insects "thrips," a name,
however, which really belongs to a very different class of insects.
The injury done by this pest varies greatly with the season and the
locality, in some regions it being comparatively harmless and in
others exceedingly destructive in seasons when it occurs in abundance.
There is great variation also in individual vineyards, those near
favorable hibernating places and early spring food plants often being
injured seriously season after season in succession. These
leaf-hoppers obtain their food by piercing the epidermis on the under
side of the leaf surface and sucking the sap, and add further injury
by inserting their eggs underneath the skin of the leaf. The punctures
greatly decrease the starch-producing area of the leaf with the result
that the vigor of the plant is lowered, and the quality of the fruit
decreased.

[Illustration: FIG. 41. First four stages of the grape leaf-hopper.
(Enlarged.)]

[Illustration: FIG. 42. The fifth and the mature stages of the grape
leaf-hopper. (Enlarged.)]

The life history of the leaf-hopper is very well known. The eggs are
deposited in June or early July, and hatch from June 15 to July 10 in
New York, the season being earlier or later as one goes south or
north. The young leaf-hoppers are wingless, the nymph stage, but reach
the adult stage in late July and August, at which time many of them
mate, and eggs are laid from which a second brood may develop,
although usually only one full brood is produced in a season in the
northern states. Figures 41 and 42 show the several life stages of the
leaf-hopper. Insects which become adults in the latter part of July
feed on the foliage until autumn and then seek winter quarters,
passing the winter in the adult stage under fallen leaves, in dead
grass or other similar protection. The hibernating place must be dry
and for this reason sandy knolls are most favored by the insects. The
adults emerge in the warm days of spring and then seek food first on
the strawberry, then migrate to red and black raspberries or
blackberries, if raspberries are not present. They remain upon these
hosts until the grape leaves expand and then migrate to these to feed,
lay their eggs and die.

Three methods of control are in use to prevent the ravages of the
leaf-hopper: avoidin