14 LEAFHOPPERS AFFECTING CEREALS, ETC. 
culty to distinguish in deadened spots on the leaves whether the pri- 
mary cause was insect or fungus. 
Still another phase of injury is to be noted in the effect produced 
upon a seed crop by the attacks of leafhoppers on the blossom or the 
newly forming seed. Puncture of the unfertilized blossom will easily 
make the pollination useless, as will also the suction of a small portion 
of the sap from a newly set seed cause it to wither or prevent its 
maturity. Injuries of this sort in wheat, timothy, clover, alfalfa, 
etc., are probably of much greater frequency than we are aware. 
Whatever view we may take as to the extent of damage and relative 
importance of these insects, all who have studied the subject will agree 
that the puncturing of the tissue and pumping of the plant juices 
must result in more or less loss and drain on the plant. The impor- 
tance then will rest on the abundance of the insects that may attack 
any particular plant. It is evident that an insect which simply 
pumps away the juices of the plant may go on with tins operation, 
constantly draining the plant and reducing its rate of growth. Still, 
unless passing the point where the drain begins to cause actual wilt- 
ing, withering, or unhealthy condition, it may attract no attention 
from the cultivator. Nevertheless, this drain must show in reduction 
of crop, less available pasturage or forage, and actual loss none the less 
real because difficult to estimate in dollars and cents. 
In some estimates based on the abundance of insects actually col- 
lected in given areas I have claimed that from 25 to 50 per cent 
of the growth of grass may go to feed these leafhoppers and still all 
this loss may occur without meadow or pasture actually showing 
by wilted or withered plants that such a drain was occurring. Only 
in periods of drought and when this loss may commonly be charged 
against a dry season is the effect such as to be noticeable in meadows 
and pastures. 
Some idea of the number of these insects can be gained from various 
observations and counts and some appreciation of it by walking 
through a pasture or meadow and noticing the clouds of minute leaf- 
hoppers that spring into the air in one's pathway. Estimates based 
on various captures in Iowa resulted in from a half million to a million 
insects per acre. In tests of the hopperdozer in catching them, the 
writer secured in some instances more than a million per acre, and 
obviously this number must fall short of what were actually present. 
Some careful estimates based on actual captures over plats 5 yards 
square were made at my suggestion in the autumn of 1908 by Mr. 
V. L. Wildermuth, now an assistant in the Bureau of Entomology. 
These were in timothy and bluegrass-timothy pastures, and while it 
can not be assumed that all the leafhoppers occurring in the given 
area were caught, the average for all these captures gives us a result 
of about a million per acre. The detailed statement of catches and 
