1957] 
Marks — Food Fumy of Hemiytera 
133 
If, however, one compares the lateral views of the arma- 
tures (Plate 11, Figs. 2 and 4) of Notonecta and Pelocoris, 
one is forcefully struck by the similarity of the transverse 
bars in these two groups. So striking is this similarity 
that the author carefully rechecked the positions of the 
muscles in relationshp to the frontal ganglion. The question 
then arises as to whether, in spite of the difference in the 
origin of the muscles attached to these bars, they are not 
actually homologous. It is possible that the present muscu- 
lature of this bar in Notonecta may be a secondary condition 
due to a posterior shifting of a group of the cibarial dila- 
tors. This would account for the position of the frontal 
ganglion as well as the reduction of the pharyngeal dilators 
to their present condition. If this were the case, then the 
transverse bar of Notonecta would be homologous with the 
posterior transverse bar of Hesyerocorixa and the trans- 
verse bar of Pelocoris. All three of the bars would be phar- 
yngeal in origin. The anterior transverse bar of Hesyer- 
ocorixa would then be homologous with the second tooth- 
bearing fold found in the transverse fold of Pelocoris, both 
being definitely cibarial in origin. At the present time there 
is not sufficient evidence available to uphold or eliminate 
either of these hypotheses. 
Certain of these relationships do, however, appear to 
be significant. Certainly the appearance of such similar 
structures in closely related groups can scarcely be coinci- 
dental. These structures then should be of some significance 
in ascertaining the relationships between groups. From 
the very slender evidence available at this time, it would 
appear that Pelocoris shows features pertaining to both 
the notonectids and corixids. It is like Notonecta in such 
features as the single, heavy, toothed bar, and the well 
developed pharyngeal pulsatile area, while it is more like 
Hesyerocorixa in the presence of secondary toothed folds 
and the highly developed cibarial pulsatile region. 
This evidence, inconclusive as it is, tends to bear out 
the suggestion of China (1955) that the Naucoridae occupy 
a place in the phylogeny of the Hemiptera which gives 
them fairly recent common ancestry with the Notonectidae 
