THE MOUTH - PARTS OF SOME BEETLE LARV7E. 
389 
the lab ram there is an arch of small spines, at the crest of 
which are six small teeth (t.J, which correspond in position 
to the six little teeth on the labrum of Helodes (PI. 35, 
fig. 10). Posterior to the median sclerite occur two short 
stout teeth (Z. 2 ) just at the middle line. Lateral to these are 
two curved bundles of spines (Z.), which may correspond to the 
two toothed lobes (PI. 36, fig. 19, Z.) on the labrum of Dascillus. 
In the strongly developed condition of the cuticle composing 
the labrum, and in its marked asymmetry, Geotrnpes is 
strikingly analogous to Dascillus. Whether the asymmetry 
of the labrum has any connection with the feeding habits of 
the larva is a point which still needs elucidation. Geotrupes, 
however, is a dung-eater, while Dascillus and Phyllopertha 
(see below, pp. 391, 392) feed on roots. 
Maxillulae and Hypopliarynx. (PI. 37, fig. 24.) 
The hypopharynx lies somewhat obliquely in the mouth, 
being connected anteriorly with the labium by a definite 
suture (text-figs. 3, 4). The basilar membrane turns back 
dorsally to line the roof of the mouth cavity, being pierced at 
the back of the mouth by the opening of the gullet (Text- 
fig. 3). 
The hypopharynx is strongly chitinised. It has a rough 
superficial symmetry, which disappears on close examination. 
The anterior region is composed of tough transparent 
chitin, forming a boss beset with spines, which is united 
with the spined margin of the labium, being marked off from 
it by the aforementioned suture. The region behind this 
boss is very strongly chitinised and bears two stout teeth 
(Z. 3 , Z. 4 ) and two lateral group of spines (mxl.). Posterior to 
this region the hypopharynx is continued into a finely 
chitinised basilar membrane, which is longitudinally ridged 
and very finely striated. 
There is an interesting general resemblance between this 
tongue and that of the Dascillus larva (PI. 36, fig. 20). The 
anterior boss may be compared to the anterior lobes of the 
latter (fig. 20, Z.Z.). The two large teeth (Z. 3 Z. 4 ), though very 
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