. Elementary text-book of zoology. Zoology. 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 flagelluni (Apis). The following structures enter into the formation of the mouth parts:—the upper lip (labrum), the upper jaws (mandibles), the first pair of maxilla1 or lower jaws, the second pair of maxilla? 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 u
. Elementary text-book of zoology. Zoology. 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 flagelluni (Apis). The following structures enter into the formation of the mouth parts:—the upper lip (labrum), the upper jaws (mandibles), the first pair of maxilla1 or lower jaws, the second pair of maxilla? 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 light and left are the mandibles or upper jaws, in the form of two 2>(^pless biting plates; they are unjointed, and therefore more powerful as masticatory organs. The .first pair of maxilla? or lower jaws have a more complicated structure. They are composed of several joints, and are, there- fore, adapted for los powerful but more varied move- ments in aid of the masticatory process. The maxilla? 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, St) with an external scale (squama palpigera), to which is attached a many-jointed palp (paljms maxillaris, Jlxt.). Two blades, an internal and external, are attached to the distal end of the second joint [and known respectively as lacinia and galeci\ (lobus externus, internus, L. in, L. ex). The maxilla? 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 first maxilla? 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 all the elements of the first maxilla- can be shown to exist (Orthop-. Lr FIG. 430.—Mouth parts of a lilatfii (after Savifmy). ", Head seen from the
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
