18 THE SUGAR-CANE INSECTS OF HAWAII. 
such a condition will then throw out sprouts from the eyes. This is 
a serious circumstance, since the growth of the sprouts is supported 
by the stalk, and unless the cane is soon cut and ground the stalk is 
rendered worthless. 
CHARACTER OF INJURY TO THE CANE. 
The first injury to the cane plant by the leafhopper occurs through 
the piercing of the epidermal layer by the ovipositor (fig. 1, b) of the 
female and the later rupturing of the tissue of the plant on the hatch- 
ing of the young. This injury to the tissue in itself is not serious, 
but the many openings in the leaves and stalks allow excessive 
evaporation to occur. Through these wounds various diseases may 
also gain entrance to the tissues of the plant, carried thereto by the 
leafhoppers themselves in flying from infested to noninfested plants, 
or by other insects, particularly certain flies, which frequent the 
cane plant. | 
The most serious injury to the plant is the drain upon its vitality 
caused by the young leafhoppers in feeding. The structure of the 
mouthparts of the leafhopper has been mentioned; that is, a piercing 
organ, which is inserted through the outer covering of the tissue, by 
means of which the insect sucks the juice or sap from within. The 
amount extracted in this manner by any particular individual is small 
and of little consequence, but the result of a myriad of individuals work- 
ing constantly in this manner upon a plant is readily conceived to be 
serious in its consequences. The leafhopper in feeding upon the 
cane plant extracts therefrom an amount of juice greatly in excess | 
of its own needs for development. This excess is excreted from the 
body of the insect upon the cane plant in the form of a sweet, sticky 
substance, known as honeydew. It is in this substance that the 
black smut develops. 
The sooty covering or smut of the leaves referred to is a super- 
ficial fungus which bears a close resemblance to the fungi of the genus. 
Spheronema. The writer was informed by Dr. A. F. Woods, at that 
time Pathologist of the United States Department of Agriculture, 
that this fungus may be responsible for the dying back of canes 
which followed heavy leafhopper infestation. It is believed, how- 
ever, that in the cane the smut affects the plant only by preventing 
the assimilation of the elements taken up by the plant from the soil 
as food, in cutting off the rays of direct sunlight, and also in closing 
the stomata of the leaves, preventing the entrance and escape of 
carbon dioxid and oxygen, respectively. In damp localities another 
fungus was taken in company with the smut, and was determined 
by Dr. Woods as a species of the genus Hypochnus. The resulting 
injury to the plant from the leafhopper attack is also complicated by 
