Noland—Anatomy of Troctes Divinatorins Muell. 
197 
maxillary in origin as Burgess concluded, or does it represent the 
inner lobe or lacinia of the maxilla, as claimed by Enderlein f 
The head of Troctes is flattened dorso-ventrally with a large pro¬ 
jecting clypeus filled with muscles which move the oesophageal 
sclerite. The internal support of the head is given it by the ten¬ 
torium (fig. 1), which consists of a central plate and two pairs of 
arms; the anterior ones (fig. 1, a.t.) arise from the head capsule 
at the point of attachment of the mandibles, and the posterior pair 
(fig. 1, p.t.) appear to arise from the head capsule posterior to the 
muscles attaching the mandibles and maxillary fork to the posterior 
wall of the head in the occipital region. 
In Troctes the inner surface of the clypeus, rather than the 
labrum as in Psocus, is furnished with tufts of hair (fig. 15, c.h.), 
and the labrum extends downward from the clypeus to meet the 
labium. The mandibles (fig. 2), heavy, chitinized structures, lie 
beneath the labrum. The dorsal portion of their inner or mesad 
surface is molar in nature for crushing (fig. 2, m.s.), while the 
ventral edge is made up of three sharply pointed teeth (fig. 2, 
v.p.), heavy enough to provide a satisfactory cutting surface. 
The dorso-lateral angle of each mandible is adapted to serve as 
the point of attachment to the lateral wall of the head capsule. 
The middle part of this area is rounded into a knob (fig. 2, m.p.) 
which fits into a corresponding socket in the wall of the capsule. 
Ventral to this is another projection (fig. 2, a.ab.) from which a 
small abductor muscle passes into the head just ventral to the base 
of the antenna. The mesad dorsal surface of the mandible is in¬ 
dented slightly (fig. 2, a.ad.) to form the point of attachment for 
a chitinous rod (fig. 1, c.m.) which is held in place by tendons. 
This rod spreads out posteriorly into several large bundles of 
adductor muscles (fig. m.m.) which fill a great part of the head 
cavity and are inserted in the posterior wall of the head. The 
maxillae and maxillary forks lie between the mandibles and labium. 
Each maxilla proper is composed of a main stipes (fig. 5, s.) which 
supports a four-jointed maxillary palp (fig. 5, m.p.) and a broad 
galea (fig. 5, g.). Burgess (6) describes a cardo in Psocus, but in 
Troctes this was not found. The inner edge of the galea is chitin¬ 
ized and has a few blunt teeth or ridges. This structure may be 
swung on the stipes by means of two muscles extending to the 
outer edge of the stipes (fig. 5, gme. and gmf.). The first muscle, 
attached to a place on the stipes anterior to the second, serves as 
the extensor, pulling the galea out laterally; the second acts as a 
