Siphunculata, or Lice 



81 



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 



64. 



Pediculus showing the blind sac (6) containing the 

 mouth parts (a) beneath the alimentary canal 

 (p). After Pawlowsky. 



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. 

 Eysell has shown that, in addition, there is a pair of chitinous rods 

 which he regards as the homologues of the maxillae. 



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. 



. *j . 65. Pediculushu- 



Lice infestation and its effects are known, medi- manus, ventral as- 



. pect of male. (X 10) 



cally as pediculosis. Though their continued pres- 

 ence is the result of the grossest neglect and filthiness, the original 

 infestation may be innocently obtained and by people of the most 

 careful habits. 



