1909. | ECTOPARASITES OF THE RED GROUSE. 315 
protruded, when it lies behind them. A muscle on each side of 
the esophagus runs from the anterior angle of the sclerite to the 
dorsal side of the head and brings about the movement of the 
organ. Kellogg has described in certain species a pair of oval glands 
which le ventral to the sclerite and the ducts of which unite and 
open by a common duct into the median groove of the thickening. 
These glands are very conspicuous in Goniodes, and are shown in 
several of our figures. Their function is unknown. Their ducts 
are cross-barred like a trachea. The whole sclerite is conspicuous 
and shines through as a somewhat V- or U-shaped dark area, 
visible from above. As Kellogg points out, a similar apparatus 
exists in the Psocide (Pls. XXXV., XXXVI., & XXX VIL. figs. 3, 
5, & 7). Two salivary glands on each side of the cesophagus have 
been described in many genera of Mallophaga. The ducts of all 
four unite and open into the pharynx by a common duct. 
The second maxille are so minute and feeble that we found it 
impossible to dissect them out even from macerated specimens. 
VI. The prothoracic legs.—These pair of appendages are turned 
forward and their ends normally lhe underneath the mouth. They 
doubtless take some part in feeding. Their inner ends are ap- 
proximated, so that the sternum here is but little more than 
a line. Snodgrass* records that the prothoracic legs do not 
move synchronously with either of the others or with each other. 
One often moves backward as the other moves forward, and he 
holds that they serve to guide the body. He thinks they serve 
to pull the body up the feather, the prothoracic legs pulling 
whilst the other legs push, like a man climbing a rope. 
VII. The mesothoracic legs.—These are larger than the pre- 
ceding and are directed backwards ; their bases are further apart. 
The details are shown in Pl. XX XIX. fig. 10. All the legs end 
in claws and bear a well-marked pulvillus. 
VIII. The metathoracic legs.—These are still larger and, like 
the preceding, are directed backwards; the sternum between their 
bases is rather wider. The right and left mesothoracic legs move 
forward simultaneously and backward simultaneously, and so do 
the right and left metathoracic legs; but when the mesothoracic 
legs move forward the metathoracic legs move backwards, and 
vice versa. 
In their general structure there is little beyond size in which 
the legs differ. Each consists of a coxa firmly applied to the 
ventral surface of the thorax; it is a broad, short piece, wide 
distally. The second article is a small trochanter which joins the 
hinder end of the wide coxa and seems to be almost part of the 
femur, but there is a marked thinning of the cuticle between it 
and the femur and a clear joint. 
The femur with the trochanter and the next article or tibia 
* Toc. cit. p. 152. 
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