Next come the mouth parts, which may be run over very quickly, for those of Beetles are formed upon the same plan, and from this primitive plan are derived the mouth parts of all other Insects, of whatever character they may be. To examine the mouth organs the insect must be turned on its back, and the _labrum_ (_a_), or upper lip, raised with a needle, so as to allow of a general view of the rest. Then the jaws or mandibles (_b_) may be picked out with a needle. These jaws are strongly toothed, and work from side to side, and it is easy to see that they are very efficient organs. The lower jaws (_c_), or _maxillae_, lie below, and are compound organs, each being made up of several parts--the base, called the _cardo_ or hinge (not shown in the illustration, but connected at right angles by a joint with the lower part, the _stipes_). From the stipes rise the _galea_, or helmet, on the outer side; and, on the inner side, the _lacinia_, to which the name maxilla is often applied, though it properly belongs to the whole. At the base of the _galea_ is inserted the five-jointed maxillary palp, thickly set with hairs, and probably an organ of touch. [Illustration: FIG. 33.--Mouth parts of a Cockroach.] By examining the maxillae (_c_) before they are separated, and comparing them with the _labium_ (_c_) or under lip, which closes the mouth from below, it will be evident that there is no slight similarity between them. Nor is this strange: for the under lip consists of the second maxillae joined at their bases, which form the _submentum_ (_s_) and _mentum_ (_m_). (The former is the small, the latter the large white basal portion; the vertical line in the illustration shows the mental suture, and should be traced in the dead insect.) The organs in the centre constitute the _ligula_; and on each side of the labium is a three-jointed palp (_labial_), like that on the maxillae, thickly set with hairs, and with a similar function. It is well to work over the mouth parts a few times till the relation between the maxillae and the labium is seen and understood. The internal tongue (_d_) is attached to the inner side of the labium. Now, still working on the under side of the insect, the three segments of the thorax are to be made out, and one cannot fail to notice the great size of the first joint (the _coxa_) in all the legs, and that these joints seem to serve as shields to protect the under side of the thorax. Then the different parts of the legs should be traced, and compared with Fig. 23 on p. 44. The spiny armature of the tibiae is to be noticed, as are the claws, between which is a projecting lobe, though this is absent in immature specimens. We shall find that the appendages of the thorax are the same as in the Margined Water Beetle. It is well to take as little as possible on trust, and to verify everything that we possibly can.