Dr. Sharp[27] says that ‘although the tibial ears of the Locus´tidae are very perfect organs, there is great difficulty in deciding on the exact nature of their functions. They would appear to be admirably adapted to determine the precise locality from which a sound proceeds ... for the legs can be moved in the freest manner in every direction, so as to bring the drum into the most direct line of the vibrations. But as to what kinds of vibrations may be perceived, and the manner in which they may be transmitted to the nerves, there is but little evidence.’ The next Order from which we shall choose examples will be the Hemip´tera, containing the Land and Water Bugs and some other forms. Our chief concern, however, is with the Water Bugs. In this Order the metamorphosis is incomplete; the mouth is adapted for sucking the juices of plants and animals; and there are usually four wings. In the Land and Water Bugs, part of the fore wings is harder than the hind wings; in the other winged members of the Order both pairs of wings are membranous. The front wings are called hemel´ytra or halfel´ytra, to distinguish them from the el´ytra or wing-cases of Beetles, which are chitinous throughout. Fig. 41 shows the hemel´ytron and hind wing of a Land Bug, and the names given to the different parts of the front wing. [Illustration: FIG. 41.--A Land Bug (magnified). _a_, corium; _b_, clavus; _c_, membrane.] The Water Scorpion (_Nepa cine´rea_) is not difficult to procure, or to keep in confinement when it is caught. It would be straining language to call it a handsome creature, yet it well deserves careful study, on account of the wonderful modification of the first pair of legs, and it is from the resemblance of these to the pedipalps of the scorpion that the insect derives its popular name. Its length is about an inch and a quarter, from the tip of the beak, or rostrum, to the end of the breathing-tube. Its greatest width is a little over a quarter of an inch (Fig. 42). The general hue harmonizes well with the mud, but the upper surface of the abdomen is a warm red, ‘and is thick set with hair, so as to afford a very agreeable sight.’ [Illustration: FIG. 42.--Water Scorpion.]