. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. INSECTA—JAWS. 523 lobed, or crooked. In the last case the first or second joint is elon- gated forming the shaft, to which the distal and shorter joints are attached at an angle as the flagellum (Apis}. The following structures enter into the formation of the mouth parts:—the upper lip (labruni), the upper jaws (mandibles), the first pair of maxillfe or lower jaws, the second pair of maxillae or lower lip (labium). The upper lip is a plate, which is usually movably articulated to the cephal
. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. INSECTA—JAWS. 523 lobed, or crooked. In the last case the first or second joint is elon- gated forming the shaft, to which the distal and shorter joints are attached at an angle as the flagellum (Apis}. The following structures enter into the formation of the mouth parts:—the upper lip (labruni), the upper jaws (mandibles), the first pair of maxillfe or lower jaws, the second pair of maxillae or lower lip (labium). The upper lip is a plate, which is usually movably articulated to the cephalic shield and covers the mouth from above. Beneath the upper lip to the right and left are the mandibles or upper jaws, in the form of two palpless biting plates; they are unjointed, and therefore more powerful as masticatory organs. The first pair of maxillae or lower jaws have a more complicated structure. They are composed of fl several joints, and are, there- fore, adapted for less powerful but more varied move- ments in aid of the masticatory process. The maxillae of the first pair (fig. 430) are made up of the following parts : — a short basal joint (cardo, C), a longer se- cond joint or shaft (stipes, 8t) with an external scale (squama palpigera), to which is attached a many-jointed palp (palpus maxillaris, JLxt.). Two blades, an internal and external, are attached to the distal end of the second joint [and known respectively as lacinia and galea] (lolus externns, interims, L. in, L. ex). The maxillae of the second pair arise from the throat, and are partially fused together across the middle line so as to form the unpaired lower lip or labium. It is rarely the case that all the parts of the fir»t maxillae are discernible in the labium, the fusion being generally accompanied by the reduction and dis- appearance of certain parts. There are, however, cases in which a,ll the elements of the first maxilke can be shown to exist (Ortlwp-. Fic. 430.—Mouth parts of a Bl
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