1, Bd) are very intimately fused together to form what is called the "lower lip" or labium, a firm transverse plate representing the fused basal portions of the maxillae, which may carry a small median "ligula," representing apparently the fused inner maxillary lobes, a pair of paraglossae (outer maxillary lobes), and a pair of palps.
A, Labium; b, maxilla; c, labrum; d, mandible.
The inner lobe (lacinia) of the first maxilla terminates in an articulated hook, while in the second maxillae (labium) both inner and outer lobes ("ligula" and "para-glossae") are much Gyrinus sulcatus reduced.
The other structural characters of the Order may be briefly summarized as: - mouth-parts adapted for piercing and sucking, or for suction alone, and consisting of a proboscis formed of the labium, and enclosing modifications of the other usual parts of the mouth, some of which, however, may be wanting; a thorax fused into a single mass; and legs with five-jointed tarsi.
The maxillae of the hinder pair become more or less fused together to form a " lower lip " or labium, and the segment of these appendages is, in some insects, only imperfectly united with the head-capsule.
The second pair of maxillae are more or less completely fused together to form what is known as the labium or " lower lip."
In specialized biting insects, such as beetles (Coleo C ptera), the labium tends to become a hard transverse plate bearing the pair of palps, a median structure - known as the ligula - formed of the conjoined laciniae, and a pair of small rounded processes - the reduced galeae - often called the " paraglossae," a term better avoided since it has been applied also to the maxillulae of Aptera, entirety different structures.
This second pair of maxillae (or labium) form then the hinder or lower boundary of the mouth.
A median process, known as the hypopharynx or tongue, arises from the floor of the mouth in front of the labium, and becomes most variously developed or specialized in different insects.
A, anus; Abx 1 Abx 11, appendage of 1st and of 11th abdominal segments; Ans, anal piece=telson or 12th abdominal segment; Ant, antenna; De, deuterencephalon; Md, mandible; Mx1, first maxilla; Mx2, second maxilla or labium; 0, mouth; Obcl, rudimentary labrum and clypeus; Pre, protencephalon; St t, Stu), stigmata i and io; Terg, tergite; Thx1, appendage of first thoracic segment; Tre, tritencephalon; Ul, a thickening at hinder margin of the mouth.
The mouth parts are well developed, consisting of an upper lip, powerful mandibles, maxillae with three-jointed palpi, and a deeply quadrifid labium or lower lip with three-jointed labial palpi.
The head of the insect contains a muscular pharynx by means of which the blood from the wound inflicted by the proboscis (labium) is pumped into the alimentary canal and the so-called sucking-stomach.
E, First maxilla; a, cardo; b, stipes; c, galea; d, lacinia; e, palp. B, Second maxillae (Labium); a, mentum; b, ligula (between the two galeae); c, c, palps.
B, c) with a deep groove on its anterior face; this organ is formed by the second pair of maxillae and corresponds therefore to the labium or " lower lip " of biting insects.
The tenth abdominal segment carries a pair of jointed cerci which are often elongate, and the feelers are always long, while the jaws are usually feeble and membranous, though the typical parts of a mandibulate mouth are present - mandibles, maxillae with inner and outer lobes and palps, and second maxillae (labium) whose lacinae are not fused to form a ligula.
Structurally the Neuroptera are distinguished by elongate feelers, a large, free prothorax, a labium with the inner lobes of the second maxillae fused together to form a median ligula, membranous, net-veined wings without hairy covering, those of the two pairs being usually alike, the absence of abdominal cerci, and the presence of six or eight Malpighian tubes.
The round ligament is a cord of unstriped muscle which runs from the lateral angle of its own side of the uterus forward to the internal abdominal ring, and so through the inguinal canal to the upper part of the labium majus.
The Dermaptera and the Orthoptera agree in having welldeveloped mandibles, so that the jaws are adapted for biting; in the incomplete fusion of the second maxillae (which form the labium) so that the parts of a typical maxilla can be easily made out (see the description and figures of the cockroach' g.
The lip--labium, from labor (?)--laps or lapses from the sides of the cavernous mouth.