THE MOUTH-PAKTS OF SOME BEETLE LARVJE. 
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fully developed on tlie molar surface of tlie mandible of the 
Dascillus larva. 
The mandible articulates with the head skeleton dorsally 
by means of the ginglymus (fig. 3, g.), and ventrally by 
means of two condyles (fig. 10, C\ and C 2 ). The ginglymus 
works on the condyle on the ventral head skeleton (PI. 35, 
fig. 10, C 3 ). The condyle C 1 corresponds to the condyle 
ordinarily found on insect mandibles, and works against the 
side of the head skeleton, but C 2 is an extra condyle below 
the molar surface, working against a strong tooth on the 
epipliarynx. An analagous structure was not found in any 
of the other larvse examined. 
Thus in the process of grinding, the molar surfaces of the 
mandibles must not only work against each other, but also 
against these strong teeth on the epipliarynx, and so the 
food must be most efficiently ground. 
Maxiliulse and Hypopliarynx. (PI. 35, figs. 11, 12.) 
The maxillulse, hypopharynx (or tongue), and labium are 
very closely associated, and rather difficult to separate with- 
out injury. They are shown in fig. 11 in situ from the dorsal 
aspect. 
The maxillula ( mxl .) is a small globular lobe projecting 
outside the edge of the labium and articulating with a con- 
dyle {con.) on the hypopharynx {hyp.). The surface of the 
maxillula is covered with parallel rows of very minute teeth, 
and on its inner edge occur a dozen or more curved teeth (£j). 
The organ ends, as Rolph (loc. cit., pi. i, fig. 31) cl early 
showed, in a sharply pointed apex covered with sensory hairs 
(fig. 12). The presence of the apex projecting beyond the 
labium, and the distinct articulation with the hypophaiynx, 
confirm the view that this structure is a true appendage. 
This is very important, for it shows beyond doubt that the 
homologous toothed lobes on the hypopharynx of Dascillus 
are maxillulae. 
The hypopharynx {Hyp.) is formed of a number of complex 
