1957 1 Marks — Food Pump of Hemiptera 131 
them. The reader is referred to the beautifully illustrated 
work of Benwitz (1956), and to the papers of Griffith 
(1945), Rawat (1939), Sutton (1951) and Marks (1958) 
for further information on these three groups. Since the 
subject of this paper is Peiocoris , it will serve as a point of 
reference and the other forms will be compared with it. 
The cibarial portion of the food pump of Peiocoris is 
elongated as it is in the Gorixidae, both groups having an 
elongated clypeal region. Correspondingly, in both groups 
the musculature of the cibarial region is highly developed 
and this region has assumed the largest part of the pumping 
function. In Notonecta, however, the clypeal region is rela- 
tively much shorter, and these muscles are only weakly 
developed. The pumping action is shared approximately 
evenly with the posterior pharyngeal pump. In all three 
insects there is a lateral oblique fold (Plate 11, Figs. 5, 6, 
and 7). This fold is figured by Rawat (1939) in Naucoris 
but is not mentionened in the text. It is not provided with 
muscles and appears to be a stiffening device enabling the 
entire membrane to respond to the pull of the muscles as 
a unit. Unfortunately Rawat’s otherwise fine paper does 
not cover the pump of Naucoris in any detail. 
The sclerotized armature is found posterior to this fold. 
In Notonecta the sclerotized, toothed bar is activated by a 
set of muscles which are apparently located anterior to 
the frontal ganglion (Griffith 1945). The position of this 
ganglion has been confirmed in this study. These muscles 
presumably represent the posterior cibarial dilators. In 
Peiocoris there is a strikingly similar toothed bar. The 
muscles which operate this latter bar, however, are behind 
the frontal ganglion and thus presumably represent the 
anterior pharyngeal dilators, raising some doubt that these 
two bars are actually homologous. In Hesperocorixa wher^ 
there are two sets of bars (Plate 11, Fig. 7), the anterior 
bars are activated by the posterior cibarial dilators while 
the posterior set is activated by the anterior pharyngeal 
dilators, the frontal ganglion being located between the 
two apodemes- Sutton (1951) reports finding two types of 
food pumps in Naucoris . She describes the first type as 
follows: “Buccopharyngeal teeth are present, so similar in 
