In all insects the body is divided into three well-marked portions (Fig. 2): the head (Figs. 4 and 5), which contains the mouth-organs, the eyes, both the compound and when present the simple, and the antennæ; the thorax, which is composed of three rings, and gives support to the one or two pairs of wings, and to the three pairs of legs; and the abdomen, which is composed of a variable number of rings, and gives support to the external sex-organs, and when present to the sting. Within the thorax there are little more than muscles, as the concentrated strength of insects, which enables them to fly with such rapidity, dwells in this confined space. Within the abdomen, on the other hand, are the sex-organs, by far the greater and more important portions of the alimentary canal, and other important organs. ORGANS OF THE HEAD. Of these the mouth organs (Fig. 6) are most prominent. These consist of an upper lip--labrum--and under lip--labium--and two pairs of jaws which move sidewise; the stronger, horny jaws, called mandibles, and the more membranous, but usually longer, maxillæ. The labrum (Fig. 6, _l_) is well described in the name upper lip. It is attached, usually, by a movable joint to a similarly shaped piece above it, called clypeus (Fig. 6, _c_), and this latter to the broad epicranium (Fig. 6, _o_), which contains the antennæ, the compound, and, when present, the simple eyes. The labium (Fig. 15) is not described by the name under lip, as its base forms the floor of the mouth, and its tip the tongue. The base is usually broad, and is called the mentum, and from this extends the tongue (Fig. 15, _a_) or ligula. On either side, near the junction of the ligula and mentum, arises a jointed organ rarely absent, called the labial palpus (Fig. 6, _k k_), or, together, the labial palpi. Just within the angle formed by these latter and the ligula arise the paraglossæ (Fig. 15, _d_), one on either side. These are often wanting. [Illustration: Fig. 6. Head of Bee much magnified. _o_--Epicranium _e e_--Compound eyes. _a a_--Antennæ, _c_--Clypeus. _l_--Labrum. _m_--Jaws. _m x_--2d Jaws. _k k_--Labial palpi, _t_--Ligula. ] The jaws or mandibles (Fig. 6, _m, m_) arise one on either side just below and at the side of the labrum, or upper lip. These work sidewise instead of up and down as in higher animals, are frequently very hard and sharp, and sometimes armed with one or more teeth. A rudimentary tooth (Fig. 21, _b_) is visible on the jaws of drone and queen bees.