L. Harrison 
117 
muscle passes from lever to integument; where it would find itself in 
company with Geocores, and the Homoptera. The more complex type, 
on the other hand, would be placed in the second division of his third 
group, forms with an extrinsic and an intrinsic muscle, including 
Periplaneta and Chrysopa. In the absence of sufficient data for sound 
comparative statement, the occluding apparatus in Mallophaga cannot 
at present be said to help towards establishing the affinities of the 
group. 
The Tracheae. 
In all forms the main trunks are two in number, and run the full 
length of the insect, one on either side of the body, from head to hind 
abdomen. Usually each of these trunks lies about a fifth of the body 
width from the lateral margin, but in most Goniodidae and Trichodec- 
tidae they are much nearer to the mid-line. They may have the appear¬ 
ance of a series of loops between the abdominal stigmata, as in most 
Amblycera ; or they may form straight trunks as in Tetrophfhalmus, 
Heterodoxus, and most Philopteridae and Lipeuridae. They vary 
considerably in diameter, as the following table shows. 
Greatest Diameter, 
IN Millimetres, op Tracheal 
Trunks. 
Oliricoln gracilis 
0005 
Lipeurus crassus 
0-01] 
Degeeriella cingulata 
OOOG 
Goniocotes gigas 
0-011 
Philopterus occidentalis 
0-006 
Tricliodectes setosus 
0-014 
Goniocotes fissus 
0-007 
Docophoroides brevis 
0-017 
Lipeurus uhsitus 
0-007 
Lipeurus feroz 
0-030 
Gyropus ovalis 
0-008 
Heterodoxus longitarsus 
0-039 
Aptericola gadowi 
0-008 
Laemohothrium circi 
0-069 
Lipeurus mutabilis 
0-010 
Tetrophthalmus titan 
0-119 
The most remarkable feature the table shows is the larg 
e size of the 
trunks in Heterodoxus and Tetrophthalmus. Heterodoxus, in common 
with other Boopidae, has large stigmata and tracheae, very like those 
of the Anoplura; and the main trunks are continuous as a posterior 
commissure, a characteristically Anopluran feature. This resemblance 
will be discussed further below. With regard to Tetrophthalnms, the 
enormous tracheae are probably a direct adaptation to the habits of 
the insect, which frequents the gular pouch of pelicans, where it must 
often be submerged for considerable periods while the host is feeding. 
Other than these enlarged trunks in Tetroplithalm^is, no tracheal dila¬ 
tations or air-sacs occur in any form which I have examined. 
