The parts of the mouth (which are named after an analogy with those of the higher animals) consist of the following pieces:--An upper lip, or _lábrum_ (fig. 25 _a_), which is squarish (quad´rate) and slightly notched; a quadrate lower lip, or _lábium_ (fig. 27), with a process on each side, and two 4-jointed lip-feelers or labial palpi (_b_); and below the labium is a chin, or _mentum_ (fig. 27 _a_), with a projecting bifid tooth: these parts form the roof and the floor of the mouth. Next come the _man´dibles_ (fig. 26), one on each side, which are stout, curved, and pointed; beneath which are the _maxil´læ_ (fig. 28), also one on each side, and provided with a fixed claw (_a_), ciliated on the inside, and furnished with two pairs of jaw-feelers, or _maxillary palpi_, the inner (_b_) being 2-jointed, while the outer (_c_) are 4-jointed. It will be noticed that the jaws work laterally, or from side to side, and not perpendicularly as in the higher animals. These parts may be found in most beetles which the observer may submit to examination, being however somewhat modified in different genera. We may consider those existing in the Lady-birds, or species of _Coccinel´la_, by way of comparison. The body in these insects is very convex, and the head sunk deeply in the thorax. The antennæ (fig. 15) are short, clubbed (clávate), and compressed. The thorax is short and lúnate, or half-moon shaped. The mandibles (fig. 13) are curved, bifid at the apex, and with a tooth on the inside near the base. The labrum (fig. 14) is transverse, or broader than long. The labium (fig. 12) is furnished with two palpi, which are 3-jointed. The maxillæ (fig. 16) are two-lobed, the lobes (_b_, _c_) being ciliated, and the 4-jointed palpi (_a_) have the last joint large and hatchet-shaped. Coleopterous insects undergo complete metamorphosis, the larvæ being commonly known as grubs. The larvæ of the aquatic beetles will often be met with in the water of ponds or ditches, especially that of the common large water-beetle (_Dytis´cus marginális_), or water-boatman as it is called (Pl. X. fig. 7), and in various stages of growth. The structure of the mouth-organs (fig. 6), which are, however, imperfect or rudimentary in some parts, can be readily made out; and their names may easily be found by comparison with what has been stated in regard to the organs of the perfect beetle.