6 
THE WESTERN CORN ROOT-WORM. 
(Diabrotica longicornis Say.) 
DESCRIPTIVE. 
The beetle may be readily distinguished from its Southern congener 
by its nearly uniform pale, but usually distinctly grass-green, or green- 
ish yellow color. (Preserved specimens usually lose this coloration to 
a considerable extent.) It is also smaller, of about the same size as 
the striped cucumber beetle, measuring about a fifth, or a little more, 
of an inch in length, and is a little more slender and less pear-shaped 
(fig. 3,a@). In the earlier stage the Western corn root-worm very closely 
resembles the Southern species, all stages naturally being smaller, as 
would be expected in an insect of smaller size. 
The egg. This applies particularly to the egg, which is of similar 
form and sculpture. It has only about 20 hexagonal pits in its longest 
diameter, compared with 30 
to 35 in that of its congener. 
It is, moreover, dirty white 
instead of yellowish, and 
measures only .015 to .025 
inch as against .02 to .03 in 
the Southern species. 
The larva, when fully ma- 
ture, attains a length of only 
four-tenths of an inch as com- 
pared with half an inch in 
Fig. 3.—Western corn root-worm (Diabrotica longi- i 
cornis): a, beetle; b, larva or root-worm; c, enlarged the case of the Southern form. 
leg of same—all enlarged, ec, more enlarged (original. ) In other respects they are very 
similar, as will be noted by comparison of the illustration of the West- 
ern species (fig. 3, b) with the Southern (fig. 1,¢). The anal segment 
in the larva under consideration is always blunt, never armed with tuber- 
culous points. 
The pupa (fig. 3, d), judging from available material, though smaller, 
is proportionately wider, giving it a more robust appearance than in the 
Southern species. 
DISTRIBUTION. 
This species, which was first recognized as a pest in 1874, has a more 
limited geographical range than the preceding, and is moreover confined 
in its field of destructiveness. We know of its occurrence from central 
New York and Canada, including Nova Scotia, westward to Kansas and 
Nebraska. Injurious occurrences are limited to the States of Illinois, 
where it is most troublesome, Indiana, Iowa, Kansas, Nebraska, Ohio, and 
Missouri. It does not occur in destructive numbers in Kentucky; in 
fact it is rarely found in that State. It was very injurious in the vicinity 
of Chillicothe, Ohio, in 1908, and injuries were reported at Circleville, 
