Anatomists have divided the human skeleton into three greater sections—the Head, the Trunk, and the Limbs. That of insects, likewise, is resolvable into three primary sections, but without including the limbs (which, as being appendages, and therefore secondary, had best be considered under the section of which they form a part), for the abdomen in insects, as well as the rest of the body, being covered with a crust, and forming a distinct part, may be properly regarded as a primary section. And in fact these three parts may be received as primary under another view—the head, as containing the principal organs of sensation; the trunk, as containing those of motion; and the abdomen, as containing those of generation[910]. Under each of these primary sections, I shall consider its respective organs, members, and parts.
You are not to expect to find every part included in the following Table in every insect; since it has been my aim to introduce into it, the most remarkable of those that are peculiar to particular tribes, genera, &c. With respect to these, I shall generally refer you to the individuals in which they may be found.
DEFINITIONS.
Corpus (the Body). The whole crust of the insect; consisting of the Exoderma or external covering, and the Esoderma or internal cuticle that lines it[911]. It is divided into three primary parts, or sections—Caput, Truncus, Abdomen.
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I. CAPUT (The Head).
The Head is the anterior section of the body; consisting of a kind of box without suture or segment, which receives the organs of sensation and manducation. It includes the Os, Facies, Subfacies, and Collum.
i. Os (the Mouth). That part of the head which receives and prepares the food for passing into the stomach. It includes the Trophi[912].
1. Trophi (the Trophi). The different instruments or organs contained in the mouth, or closing it, and employed in manducation or deglutition. They include the Labrum, Labium, Mandibulæ, Maxillæ, Lingua, and Pharynx.
A Labrum (the Upper-lip). A usually moveable organ; which, terminating the face anteriorly, covers the mouth from above, and is situate between the Mandibulæ[913]. It includes the Appendicula.
a Appendicula (the Appendicle). A small piece sometimes appended to the upper-lip[914]. Ex. Halictus ♀ Walck. (Melitta **. b. K.)
B Labium (the Under-lip). A moveable organ, often biarticulate, which terminating the surface anteriorly, covers the mouth from beneath, and is situate between the Maxillæ[915]. It includes the Mentum, and Palpi Labiales.
a Mentum (the Chin). The lower joint of the Labium, where it is jointed; in other cases its base. It is usually seated between the base of the Maxillæ[916].
b Palpi Labiales (the Labial Feelers). Two jointed sensiferous organs, the use of which is not clearly ascertained, which emerge, one on each side, from the Labium, mostly near its summit[917].
C Mandibulæ (the Upper-jaws). Two transverse lateral organs, in most insects used for manducation; generally corneous, moving horizontally, and closing the mouth above, under the Labium[918]. They include the Prostheca, Dentes, and Mola.
a Prostheca (the Prostheca). A subcartilaginous process attached to the inner side, near the base, of the Mandibulæ of some Staphylinidæ[919]. Ex. Ocypus similis K., Creophilus maxillosus K., &c.
b Dentes (the Teeth). The terminating points of the Mandibulæ. They include the Incisores, Laniarii, and Molares[920].
A Incisores (the Cutting-teeth). Teeth somewhat wedge-shaped, externally convex and internally concave[921]. Ex. Gryllotalpa Latr., Gryllus Latr. (Acheta F.), &c. &c.
B Laniarii (the Canine-teeth). Very sharp and usually long conical teeth[922]. Ex. Forficula L., Mantis L., Libellula L.
C Molares (the Grinding-teeth). Teeth that terminate in a broad uneven surface, fit for grinding the food[923]. Ex. the herbivorous Orthoptera.
c Mola (the Mola). A broad, flat, subrotund space, transversely grooved or furrowed, observable on the inner side of some mandibles that have no grinding-teeth at their apex[924]. Ex. Euchlora MacLeay, Anoplognathus Leach, Larva of Lucanus[925].
D Maxillæ (the Under-jaws). Two organs moving subhorizontally, fixed on each side at the base of the Labium, and often parallel with it—which in masticating insects seem primarily designed to hold the food[926]. They include the Cardo, Stipes, Lobi, and Palpi maxillares.
a Cardo (the Hinge). A small, transverse, usually triangular, corneous piece, upon which the Maxilla commonly sits[927].
b Stipes (the Stalk). The corneous base of the Maxilla, below the Palpus[928].
c Lobi (the Lobes). The parts of the Maxilla above the Palpus[929]. They include the Lobus superior, the Lobus inferior, and the Ungues.
A Lobus Superior (the Upper-lobe). The outer lobe of the Maxilla, incumbent on the inner one. In the Predaceous Beetles this lobe is biarticulate and palpiform[930]; and in Staphylinus olens, &c. it also consists of two joints[931]. It is called the Galea by Fabricius, in Orthoptera, &c.[932]
B Lobus Inferior (the Lower-lobe). The inner lobe of the Maxilla, covered by the outer one[933].
C Ungues (the Claws). One or more corneous sharp claws which arm the lobes of the Maxilla[934]. In the Predaceous Beetles there is only one terminating the lower lobe, with which, in Cicindela, it articulates; in the Orthoptera and Libellulina there are several.
d Palpi Maxillares (the Maxillary Feelers). Two jointed sensiferous organs, the use of which is not clearly ascertained, emerging from an exterior lateral sinus of the Maxilla[935].
E Lingua (the Tongue). The organ situated within the Labium or emerging from it, by which insects in many cases collect their food and pass it down to the Pharynx, situated at its roots above. It varies considerably in different orders and tribes. In the Orthoptera, Libellulina, &c. it is linguiform, and quite distinct from the Labium[936]; it appears also distinct in the lamellicorn beetles, &c.[937] In many Hymenoptera it emerges from the Labium, and is fitted to collect liquids and pass them downwards[938]. In Formica it appears to be retractile[939]. In a considerable proportion of insects it seems connate with the Labium, and forming its inner surface? According to circumstances it might perhaps be denominated Lingua or Ligula. It includes the Paraglossæ.
a Paraglossæ (the Paraglossæ). Lateral and often membranous processes observable on each side of the tongue in some Hymenoptera, &c.[940]
F Pharynx (the Pharynx). The opening into the gullet[941]. It includes the Epipharynx and Hypopharynx.
a Epipharynx (the Epipharynx). A small valve under the Labrum, that in many Hymenoptera closes the Pharynx, and is an appendage of its upper margin[942].
b Hypopharynx (the Hypopharynx). An appendage of the lower margin of the Pharynx, observable in Eucera F.[943]