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 
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. 
. . . 65. P e d 1 c u 1 u s hu- 
Lice infestation and its effects are known medi- manus, ventral as- 
... pectofmale. (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. 
64. Pediculus showing the blind sac (6) containing the 
mouth parts (a) beneath the alimentary canal 
( p ). After Pawlowsky. 
