. Circular. Insects. 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 closety resemb
. Circular. Insects. 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 closety 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 the case of the Southern form. 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. l,c). 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
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