93 
Distribution.— Thh beetle was introduced from Europe, where it 
has been known for more than a century, feeding chiefly on red clover 
"but also on alsike. In this country it first attract- 
ed attention as a pest in 1878 in central New 
York. Thence it spread westward in the region 
of Lake Erie, doing great damage in Ontario, 
Can., in 1888, appearing in Michigan in 1889 at 
the west end of Lake Erie, and after that spread- 
ing over southern Michigan with disastrous con- 
sequences. In Ohio it was injurious by 1890, 
and seriously so in the northwestern part of the 
state in 1893. It has reached Indiana, Illinois, 
Pennsylvania, West Virginia, and North Caro- 
lina, and has even been reported from Oregon. 
Food Plants and Injury. — In America the 
chief food plants are red clover and mammoth 
clover; others being alsike, alfalfa, and the pea. 
First-year clover, its roots being small in 
spring, when the beetle lays its eggs, is not known 
to be attacked by this borer ; second-year clover 
is attacked; and clover that has been allowed to 
run for more than two years harbors the pest in 
abundance. 
An affected plant finally wilts and dies; 
when pulled by hand or by the mower it breaks 
off at the surface of the ground. The roots of 
such a plant are burrowed out longitudinally 
(Fig. 17), the burrows, with their walls more or 
less decayed, contain the excrementitious parti- 
cles of the insect, and usually the insect itself in 
one or more of its stages, tho the beetles, being 
small, sluggish, and inconspicuous in color, are 
easily overlooked. Small cylindrical holes thru 
the sides of the roots are characteristic of this 
species, as indicating the emergence of beetles. 
The amount and rapidity of injury depend 
not only upon the number of insects present but 
also upon the amount of moisture received by the plant. In dry 
weather the plant succumbs quickly to the borer, but in wet weather 
the plant, tho weakened, may continue to survive. Injured plants are 
liable to die late in June or early in July, after cutting ; tho with plenty 
of rain many of the crippled plants may live until winter. In 1893 
and 1894 the root-borer, in combination with the leaf-weevil and dry 
weather, caused a general failure of the clover crop in Michigan. 
The borer is said to be responsible for an irregular, imperfect 
blooming of the clover or a failure to bloom at all. If the plants sur- 
vive, thanks to copious rains, the yield of seed is liable to be almost 
nothing. In central Illinois the root-borer is generally distributed, but 
Fig. 17.— Clover Root- 
borer, Hylastinus ob- 
scuriis; work of insect. 
(Webster, Circ. 67, Bur. 
Ent., U. S. Dept. of Ag- 
riculture.) 
