43 
The combined efforts of all the insects, however, are sufficient to 
reduce the hay crop materially every year. Aside from the occasional 
conspicuous injury, there is every year a steady drain on the plant 
thru the attacks of insects. This annual drain is not noticed for the 
very reason that it occurs every year. If we could keep all the insects 
out of the clover field, we should get more hay. If we could exclude 
all except the bumblebees and the honey-bees, we should undoubtedly 
get an immense increase in the yield of seed. 
Those who raise clover seed on a commercial scale owe their suc- 
cess to methods which operate chiefly against the insect enemies of the 
seed- — whether the growers are aware of it or not. Under the same 
conditions of soil and climate, one man is able to get a good crop of 
seed and his neighbor is not. The reasons for this are chiefly entomo- 
logical, as appears in these pages. 
The Failure of the Seed Crop 
Many farmers do not attempt to raise their own clover seed. 
Those who do. get more or less of a crop according to circumstances. 
Here in the black soil of the corn belt, 1^ bushels of seed per acre is 
about the average yield for red clover (Trifoliuni pratense) ; the soil 
is not the best possible for clover ; frequently too little seed is sown ; 
generally the oats and the wheat are regarded as of more importance 
than the clover; and always the seed insects ravage the crop unless 
certain precautions are taken. In DeKalb county the soil is better 
adapted to clover, and, tho the winter conditions are now and then a 
little severe for the plant, the farmer expects to get about five bushels 
of seed to the acre by cutting the hay crop early. Under the most 
favorable conditions, red clover has yielded eight bushels per acre ; I 
have found records of nine, but the more authentic accounts name no 
more than eight. 
Many influences, more or less important, combine to reduce the 
crop of seed. Adverse mechanical or chemical conditions of the soil, 
or unfavorable conditions of the weather, may prevent the plant from 
flowering properly. With good conditions of soil and weather, the gen- 
eral health of the plant may be impaired by fungous diseases of several 
kinds or by insects, particularly the root-borer, the leaf-weevil, and the 
clover-louse ; their devastations cause the heads to flower unevenly and 
imperfectly, and prevent the formation of a large number of heads in 
the crop directly attacked by them. 
These injuries, due to influences that affect primarily the general 
health of the plant and secondarily the seed, are easily referable to 
their respective causes. The worst injuries to the seed are more in- 
sidious in their nature, and are caused by insects. These injuries are 
of three classes: (1) those of a negative kind, due to lack of pollina- 
tion; (2) the positive injuries due to miscellaneous insects that eat 
clover heads in an incidental way; (3) the positive injuries caused by 
insects that feed solely upon clover seeds or florets. The first two 
groups are relatively unimportant in comparison with the last. 
