important character of having a sucking instrument with a jointed sheath, and it must be admitted to be highly inadvisable to multiply orders except for the most urgent reasons. But if rejected as primary groups, they must be adopted as secondary ones; and we shall accordingly follow Latreille, who has, from this circumstance, divided this order into two great sections, which he denominates Heteroptera (wings of different texture) and Homoptera, (wings of uniform texture.)
The under wings are usually not of large size, and offer nothing peculiar in their forms and composition. When at rest they are covered by the hemelytra, being simply drawn beneath them, and more or less crossed, but without forming distinct longitudinal or transverse folds. Several species of Hemiptera are entirely apterous.
This is the only order in which upper wings of a rigid consistency coexist along with a mouth formed for sucking. The latter differs considerably from the spiral tube of butterflies and moths, which is a mere canal for conveying the nutritive fluids into the esophagus; besides serving this purpose, it is so formed that it acts as a lancet for piercing the integuments of plants and animals. As great length would scarcely be compatible with such a usage, it seldom equals the dimensions of a lepidopterous proboscis, being usually much shorter than the body. There are a few exceptions to this rule, however, and in some examples it is so long as to project a good way behind the body like a caudal filament. Although so different in ap-
