OF SUCTION IN LYGUS PABULINUS. 
695 
epicranium and clypeus, is not well marked.) The sides of the 
clypeus have sunk into the head, forming clypeal folds to which 
the protractors of the mandibles are attached, and which are 
fused with the ventral wall of the pharynx (text-fig. 17, Clp.F.). 
(8) The Labrum.—tThis is merely a continuation of the clypeus, 
and there is no sign of external differentiation between the two 
structures. 
It extends as far as the first segment of the labium, 
and tapers to a point, the base being broader. 
It has rather a 
deep groove underneath to hold the stylets in place, since the 
labial groove at this point is too shallow and flat to do this. 
There are three external longitudinal ridges on its dorsal surface ; 
its sides are ornamented with small rounded lobes, and its surface 
Explanation of Lettering. 
. Antagonistic Muscles. 
. Afferent Salivary Duct. 
. Anterior Wall of the Pump- 
chamber. 
- Buccal Fold. 
. Cambium. 
. Circumesophageal Com- 
missure. 
p. Clypeo-labrum. 
». Clypeo-labrum. 
. Clypeal Fold. 
. Clypeal Sclerite. 
. Constrictor Muscles. 
. Cortex. 
. Cribriform Plate. 
. Cardiac Valve. 
. Dorsal Arms of the Ten- 
torium. 
. Divaricator Muscles. 
. Ejection Canal. 
. Epicranium. 
Epidermis. 
. Epipharynx. 
. Endodermis. 
. Efferent Salivary Duct. 
», Gustatory Organs. 
. Hypopharynx. 
. Lumen of the A.S.D. 
. Labium. 
. Labial Groove. 
. Labial Muscles. 
r, Labrum. 
. Ligament for A.M. 
. Ligament for D.M. 
. Ligament for P.M. 
. Mandibles. 
. Mandibular Articulation. 
. Mandibular Lever. 
. Protractors of the Man- 
dibles. 
. Retractors of the Man- 
dibles. 
. Cavity of the Mandibles. 
. Hooks of the Mandibles. 
. Mandibular Sheath. 
. Mouth of the A.S.D. 
| 
Mx.C. 
Mx.F. 
Mx.L. 
Mx.P. 
Mx.R. 
Mx.Md. Art. 
Mx.Md.M. 
Cavity of the Maxillary 
Stylet. 
Maxillary Fold. 
Maxillary Lever. 
Protractors of the Maxillary 
Stylets. 
Retractors of the Maxillary 
Stylets. 
Maxillo - mandibular Arti- 
culation. 
Maxsillo - mandibular 
Muscles. 
Sc. Maxillary Sclerite. 
. Maxillary Sheaths. 
. Maxillary Stylets. 
. Operculum. 
. (sophagus. 
. Posterior Arms of the 
Tentorium. 
y. Pump-cylinder. 
. Pump-chamber. 
. Piston. 
. Handle of the Piston. 
. Pharyngeal Duct. 
. Pharynx proper. 
. Phloem. 
. Pump Muscles. 
. Retort-shaped Organs. 
. Pump-stem. 
. Posterior 
Wall of the 
Pump-chamber. 
. Maxillary Process or Sup- 
porting Strut. 
. Suction Canal. 
. Supra - esophageal Gang- 
lion. 
. Sub-cesophageal Ganglion. 
. Salivary Duct. 
. Body of the Tentorium. 
. Trachea. 
<. Tip of the Maxillary Stylet. 
. Tip of the Mandible. 
. “V” or ventral wall of the 
Pharynx. 
. Valvular muscles. 
. Xylem. 
