The entomologist's text book : an introduction to the natural history, structure, physiology and classification of insects, including the Crustacea and Arachnida . the tyj)ical structm-e ofannulose animals in general—a vast and difficult subject ofinvestigation. We will, therefore, now confine our atten-tion to A.—The Head, or the Seat of the Organs of Sensation. The head, or first segment of the body, is united tothe anterior part of the thorax by a distinct articulation,and may be considered as a kind of corneous case or box,having an opening in the centre of its anterior part, wherethe mout
The entomologist's text book : an introduction to the natural history, structure, physiology and classification of insects, including the Crustacea and Arachnida . the tyj)ical structm-e ofannulose animals in general—a vast and difficult subject ofinvestigation. We will, therefore, now confine our atten-tion to A.—The Head, or the Seat of the Organs of Sensation. The head, or first segment of the body, is united tothe anterior part of the thorax by a distinct articulation,and may be considered as a kind of corneous case or box,having an opening in the centre of its anterior part, wherethe mouth is placed. It is of a triangular or oval shape,with the narrowed part advanced in front; the middle of the X 230 PTILOTA : IMAGO—EXTERNAL ANATOMY. opposite side, or base, being occasionally prolonged into aneck; but there are numerous modifications of this form,and the head is often buried as far as the eyes in the pro-thoracic cavity. On minutely examining the skull, it will befound that it consists of several regions. These are, theepicranium or skull-cap, composing the greater part of thehead, of w^hich it chiefly occupies the upper and posterior. Figs. 53, Head of Dyti -54, ditto Oxycheila—55, ditto Heliocantharus—56, dittoAcantliotliorax. part. This is bounded in front by the clyj^eus (c), or shieldof the mouth, which generally lies above the parts of themouth (m), and the under side of the head is covered by thejugulum, or throat. At the sides of the epicranium are situ-ated the large compound eyes (e), between which, whenpresent, the ocelli (o), or simple eyes, are placed, and theantennae (a) are inserted nearer to the mouth; but all theseparts will require a more precise examination. The head is generally of a corneous, or coriaceous texture,although at times it is membranous or vesiculose; and itsform is modified from oval, or globose, to longitudinal, heart-shaped, compressed, cornuted, rostrated, &c. The parts ofthe epicranium, and its frontal part, the c
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Keywords: ., bookau, bookcentury1800, booksubjectcrustacea, booksubjectinsects
