LEAFHOPPEKS AFFECTING CEKEALS, ETC. 13 
NATURE AND EXTENT OF INJURY. 
Like other members of the order of Hemiptera, such as the squash 
bug, the chinch bug, aphides, scale insects, etc., the leaf hoppers 
secure their food and incidentally occasion injury to the plants they 
infest by sucking the juice of the plant. The mouthparts consist of a 
beak or proboscis, inclosing slender threadlike piercing organs which 
are thrust into the plant and through which the plant juices are drawn 
into the stomach. The result is a wilting or shriveling of the plant 
cells that are thus depleted of their contents, sometimes a curling of 
the leaf or the distortion of the adjacent parts, and in some cases a 
discoloration of the surface. This sometimes becomes a factor in 
protecting the insect, especially when the color of the insect and that 
of the plant cells is the same. Probably the most familiar examples 
of this kind of work are those of the wilting noticed following attacks 
of the squash bug or the chinch bug, the whitening of grapevine 
leaves by the grape leafhopper, or the coloring and curling of leaves 
infested by plant-lice. 
On grasses and grains the attack is most commonly noticed in the 
form of wilted or discolored blotches on the leaves or stems. It was 
described by Webster as a combination of punctures and slitting. 
Sometimes, in bluegrass particularly, it results, as the writer believes, 
in the condition known as "silver top/' a whitening of the entire 
upper part of stem and head, though this particular condition is in 
some parts of the country undoubtedly due to attacks of the grass 
thrips (TJirips striatus Osb.) 1 . 
Another relation to be noted is connected with the parasitic fungi 
that are frequently associated with the leafhoppers. It seems quite 
possible that these fungi may be assisted by the leafhoppers in their 
distribution or entrance to the plant tissues. In work on the sugar- 
cane leafhopper in Hawaii the insect is credited with increasing 
attacks of the fungus. 2 
The author was informed by the plant pathologist connected with 
the Bureau of Plant Industry, United States Department of Agricul- 
ture, however, that while certain saprophytic forms might attack the 
injured spots punctured by the leafhoppers, the truly parasitic species 
like the rusts invariably attack the healthy tissue in preference to 
injured places; the leafhoppers might, however, easily be an agent in 
the scattering of the spores over the plant and hence become a factor 
in the increase of injury from rust. It is often a matter of much diffi- 
1 See article "Silver top in grass and the insects which produce it." Osborn, Can. Ent., vol. 23, pp. 93- 
96, 1891. 
2 See "Fungus Maladies of Sugar Cane," by N. A. Cobb. Exp. Sta. Hawaiian Sugar Planters' Assn., 
Bui. B, Div. Path, and Phys. Also "Rind Disease of Sugar Cane." Bui. 7, Hawaiian Sugar Planters' 
Assn. A similar condition is presented in the fungus rice blast, which, according to Mr. H. R. Fulton 
(La. Exp. Sta., Bui. 105, Apr., 1908), gains entrance to the plant tissue through punctures of (Ebalus 
pugnax Fab. 
