HEMIP´TERA (ἤμισυς, half, πτερὀν, wing).--This Order contains the bugs and other noxious insects. Those which we shall notice are the species of _A´phis_, commonly known as Plant-lice and Green-fly, which are found too frequently upon unhealthy plants. The species figured (Pl. X. fig. 2) is that of the geranium (_Pelargonium_). The head is small and notched or emarginate. The body is oval and furnished behind with two prolonged tubercles, these being covered with scales, giving them a somewhat striated appearance (fig. 2 _b_). The antennæ are 6-jointed (_c_), the second joint being very small, the last joint long, excavated on one side, and ringed: these organs are reflexed over the body in the natural state. There are two compound eyes, and three simple eyes or ocelli, forming a triangle on the top of the head. The proboscis or rostrum is bent under the body, 4-jointed, and contains three setæ, two of them forming very slender lancets. The legs are long; the tarsi (fig. 2 _a_) 2-jointed, the first or basal joint being very minute, and the last furnished with two claws. In a colony of these insects, some are winged and some wingless; those without wings being usually in the larva state, the pupæ having rudimentary wings, and the males and females usually perfect wings. _Aphis brass´icæ_ is the destructive turnip-fly. COLEOP´TERA (κολεὀς, sheath).--This, which is the last Order to be noticed, contains the Beetles, so easily recognized by their hard and horny fore wings or wing-cases. The parts of the mouth in these insects are exceedingly well adapted for examination; and as they are not fused or consolidated with each other, they serve to illustrate the typical constitution of the organs as existing in these animals. _Pteros´tichus_ (_Ster´opus_) _mad´idus_ (Pl. X. fig. 23) is common in cellars and gardens among vegetable rubbish. The body of this beetle is shining black, the head projecting; the antennæ (fig. 23 _a_) are filiform, and compressed towards the end. The thorax is somewhat rounded, with a deep rough pit and a longitudinal stria at each posterior angle. The wing-cases, or elytra, are longitudinally striated; the wings, which in most beetles are concealed beneath the elytra when the insects are at rest, being absent. The tibiæ of the fore legs are notched on the inside (fig. 24 _a_), a fringe of hairs being situated in the notch; the tarsi are 5-jointed (fig. 24 _b_), the first four joints being triangular, the last elongate and terminated by two curved claws. In the male the three first joints of the tarsi of the anterior legs (fig. 24 _b_) are dilated and heart-shaped.