718 MR. P. R. AWATI ON THE MECHANISM 
Wedde, however, thinks that they are the clypeal muscles, 
which have nothing to do with the mandibular lev ers, but whtteli 
ave attached to them. He does not seem to have understood the 
nature of the “horizontal bar,” which is nothing less than the 
mandibular lever. 
(7) The Constrictors or Circular Muscles. (Text-figs. 2, 7, 
Con.M.) 
These muscles are found in the cesophageal region. They lie 
outside the external epithelium of the cesophagus. Their con- 
traction and relaxation produce a kind of peristalsis which forces 
the sap onward into the stomach. Bugnion (4) says, “ quant au 
constricteur, son role doit étre de pousser dans lcesophage le 
liquide absorbe.” 
(8) The Valvular Muscles. (Text-fig. 7, V.M.) 
They are short and thin and extend from the base of the cardiae 
valve in the cesophagus to the posterior arms of the tentorium, to 
both of which they ave attached. When they contract, the sides 
of the valve are pulled apart, the valve thus opens, the lumen of 
‘the csophagus widens, and the sap, which is under a great 
pressure behind, is forced onward into the stomach, I cauinan 
find them described by any previous writer. 
(9) The Labial Muscles. (Text-figs. 2, 16, Lb.M.) 
These are found in the first segment of the labium, and seem 
to be important in increasing the amount of protrusion of the 
stylets by bending the labium. They are attached at one end to 
the supporting struts (buccal folds) on either side of the pump- 
cylinder, and at the other to the first joint of the labium, which is 
swollen, and thus offers a large area for the attachment of these 
muscles. 
It will be remembered that the proboscis bends upon itself, the 
bending occurring at the first joint. The deeper the required 
piant-tissue les, the greater 1s the bending of the proboscis. 
There must be some device to effect this bending, and such 
device is supplied by these labial muscles. When the muscles 
contract, the first joint is pulled up and acts as a hinge—the 
proboscis bending on it. 
According to Geise, Wedde, and Nietsche they are elevators 
and depressors of the labium. In the insect under consideration 
no muscles are found that could possibly function in this way. 
(10) Zhe Muscles of the Antenne. 
As these have nothing to do with suction, they will not be 
described. 
N.B.—Wedde has described two pairs of protractor muscles of 
the maxillary stylets, one of which is attached to the maxillary 
