THe Hoc Louse 655 
the thorax. These were described in this and other Siphuneulata 
(Anoplura) by Enderlein (1904:126), who named them “ Hinterhauptvor- 
satz”’ and thought that morphologically they probably originated as 
tendons of the retractor muscles of the head. .Mjéberg (1910: 2062-203) 
named them the “ occipital apodeme.” Gross dissection reveals the 
continuation of these processes as muscle bands having their origin- on 
the apodeme of the metathorax, while muscles controlling the lateral 
movements of the head are inserted on their posterior lateral borders. 
The dorsal surface of the thorax is strongly chitinized and the segments 
are completely fused with one another. In mature lice the sternal plate 
is present on the ventral surface. On the prothorax, and also on the 
anterior angles of the sternal plate, is a pair of very small openings 
approximately 0.03 millimeter in diameter, which are present at all stages 
of development (Plate LVIII, 6, 8, and 10) and have been passed over 
or variously described up to the present time. Stevenson (1905:15), 
in his description of the thorax, says: ‘“‘ On the ventral surface between 
the appendages is a chitinous shield. In each anterior lateral angle of 
this shield or plate is an opening calied the osteole, leading from a canal 
that extends cephalad.”” Myjéberg does not mention either of the pairs 
of openings, and Neumann (1911:407) describes “a pair of very small 
thoracic stigmata ”’> and “a small stigma in each anterior angle’’® of 
the sternal plate. Patton and Cragg (1913:548) describe both pairs of 
openings as stigmata. On the sternal plates of seventeen species of 
Siphunculata (Anoplura) figured by Kellogg and Ferris (1915: Pl. IV), no 
such openings are present. 
Gross dissection has shown that these openings are quite different from 
the stigmata of the tracheae, are without a closing device, and communi- 
cate with a canal which has no connection with the respiratory system. 
- The dorsal openings on the prothorax are connected with those on the 
sternal plate by a rigid, uniformly chitinous canal passing directly dorso- 
ventral laterad of the thoracic tracheal trunk. One short branch is given 
off almost at right angles to the main stem and at about one-third of the 
total length of the latter from its dorsal surface, and passes caudad 
terminating in the transverse band of muscle which lies between the second 
pair of legs (Plate LVIII, 12). Series of cross sections made through the 
5 Translated from the original French. 
