50 MOSQUITOES OF NORTH AMERICA 
are ordinary salivary glands and the third, between the other two, differs in ap- 
pearance and structure and secretes the poison. Each set of glands discharges 
into a very fine duct and these ducts unite in the back of the head and continue 
forward as a single duct through the ventral region of the head. Macloskie’s 
studies were made with Aédes teniorhynchus and a species of Anopheles. 
At the base of the hypopharynx is the salivary pump into which the salivary 
duct empties, to be continued beyond it into the hypopharynx. Macloskie failed 
to recognize its true character and called it the salivary “ reservoir.” Its true 
character appears to have been first recognized by Annett, Dutton, and Elliott. 
The organ is fully described by Nuttall and Shipley, from whom we quote. As 
yet the organ has only been demonstrated in Anopheles. 
“. .. The structure is more than a receptacle, it constitutes a pump, the 
mechanism of which corresponds to that of the pharyngeal pump in a sense, that 
is, it depends upon the action of powerful voluntary muscles which overcome the 
elasticity of a chitinous membrane which, when released by the muscles becom- 
ing relaxed, rebounds or returns to its original form, as a bow does when the pull 
on the bow-string is released. . . . It will be seen then that the common salivary 
duct ends (lumen 5) in the centre of the chitinous membrane, the junction be- 
ing strengthened by a chitinous thickening of annular form. The membrane is 
continuous with a highly chitinized cup, which tapers anteriorly, and is continu- 
ous with the hypopharynx, an opening therein connecting it with the groove 
described above. . . . Spicules of chitin occur about the duct on the pump- 
membrane, these serving for the attachment of the powerful muscles presently 
to be described. The thickened chitin surrounding the membrane is flattened 
on its dorsal surface which is applied to the floor of the buccal cavity. The 
pump-membrane is covered in the centre by the insertion of two stout bundles of 
muscle-fibres which pass backwards, parallel with one another, to their origin 
on the anterior surface of the chitinous flange which projects ventrally from the 
floor of the buccal cavity. When the muscles contract a partial vacuum is 
produced within the cup, saliva flows in from the glands, and when they relax 
the membrane rebounds forward, driving the saliva out of the cup into the 
salivary channel along the hypopharynx.” 
Leon, who investigated this organ independently, gives a description at vari- 
ance with that of Nuttall and Shipley. He found that the salivary duct empties, 
not into the center of the posterior membrane of the cup, as described by Nuttall 
and Shipley, but into the side of the chitinous cup. The pumping device Leon 
describes as follows: 
“The mouth of the cup, which is directed posteriorly and ventrally, is covered 
by an elastic chitinous membrane which is pushed back into the interior of the 
cup like the bottom of a champagne-bottle. Outside, in the middle of this mem- 
brane, a chitinous piston-rod is attached. This has the form of a round concave- 
convex disc and is more darkly colored ; the convex side of the disc is attached to 
the elastic membrane, while in the middle of the concave side the rod is fixed. 
. . . The posterior end of the rod is thickened and muscles are attached to it.” 
THE PALPI. 
The palpi, as they appear in both sexes of Culea, have been described in the 
foregoing in connection with the other mouthparts. Great diversities of 
opinion have been expressed by the different students as to their structure and 
