. Entomology for medical officers. Insect pests; Insects as carriers of disease. THE ORDER DIPTERA 35 the mouth-parts and even the mouth are vestigial. The proboscis is a composite structure, and the exact homologies of its component parts are somewhat problematical. It is generally assumed that the proboscis, as seen without dis- section, is the labium ; it forms a sheath for the other mouth- parts, which lie concealed in a deep groove that runs along its dorsal surface. The parts so ensheathed by the labium are not constant, as may be observed by comparing the proboscis of a female mosquito
. Entomology for medical officers. Insect pests; Insects as carriers of disease. THE ORDER DIPTERA 35 the mouth-parts and even the mouth are vestigial. The proboscis is a composite structure, and the exact homologies of its component parts are somewhat problematical. It is generally assumed that the proboscis, as seen without dis- section, is the labium ; it forms a sheath for the other mouth- parts, which lie concealed in a deep groove that runs along its dorsal surface. The parts so ensheathed by the labium are not constant, as may be observed by comparing the proboscis of a female mosquito with that of a blow-fly. In the female mosquito (Fig. 2) the labium is long and slender, and ends in a pair of small stiffish lobes, the labella. In the groove of the labium lie (i) the long pointed upper- lip, or labrum-epipharynx; and (2) the slender FiQ. 2.—Head of temale Mosquito. which is traversed in all its length by the common salivary duct. The labrum-epipharynx is grooved all along its ventral surface, and the groove is converted into a tube by the apposition of the epipharynx: up this tube the blood is drawn when the " mosquito " bites a victim. Besides these two tubes—an efferent salivary tube tunnelled in the hypo- pharynx, and an afferent suctorial tube formed by the apposition of the hypopharynx to the epipharynx—there exist two pairs of organs which are regarded as homologous with the mandibles and maxillce of insects, such as the cock- roach (Fig. 112) that feed on solid food. Both mandibles and maxillae are long, slender, flexible rods slightly broadened. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Alcock, A. (Alfred), 1859-1933. London, Gurney & Jackson
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Keywords: ., bookcentury1900, bookdecade1910, bookpubl, booksubjectinsectpests
