. Handbook of medical entomology. Insect pests; Insects as carriers of disease; Medical parasitology. Siphunculata, or Lice. 64. Pedlculus showing the blind sac (&) containing the mouth parts (a) beneath the alimentary canal {p). After Pawlowsky. reduced to a single ommatidium on each side. The short, powerful legs are terminated by a single long claw. Metamorphosis incom- plete. There has been a great deal of discussion regarding the structure of the mouth-parts, and the relationships of the sucking lice, and the questions cannot yet be re- garded as settled. The con- flicting views are w
. Handbook of medical entomology. Insect pests; Insects as carriers of disease; Medical parasitology. Siphunculata, or Lice. 64. Pedlculus showing the blind sac (&) containing the mouth parts (a) beneath the alimentary canal {p). After Pawlowsky. reduced to a single ommatidium on each side. The short, powerful legs are terminated by a single long claw. Metamorphosis incom- plete. There has been a great deal of discussion regarding the structure of the mouth-parts, and the relationships of the sucking lice, and the questions cannot yet be re- garded as settled. The con- flicting views are well repre- sented by Cholodkovsky! (1904 and 1905) and by Enderlein (1904). Following Graber, it is generally stated that the mouth-parts consist of a short tube furnished with hooks in front, which consti- tutes the lower lip, and that within this is a delicate sucking tube derived from the fusion of the labrum and the mandibles. Opposed to this, Cholodkvosky and, more recently, Pawlowsky, (1906), have shown that the piercing apparatus lies in a blind sac under the pharynx and opening into the mouth cavity (fig. 64). It does not form a true tube but a furrow with its open surface uppermost. EyseU has shown that, in addition, there is a pair of chitinous rods which he regards as the homologues of the maxillee. When the louse feeds, it everts the anterior part of the mouth cavity, with its circle of hooks. The latter serve for anchoring the bug, and the piercing apparatus is then pushed out. Most writers have classed the sucking lice as a sub-order of the Hemiptera, but the more recent anatomical and developmental studies render this grouping untenable. An important fact, bearing on the question, is that, as shown by Gross, (1905), the structure of the ovaries is radically different from that of the Hemiptera. Lice infestation and its effects are known, medi- cally as pediculosis. Though their continued pres- ence is the result of the grossest neglect and filthiness, the origina
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