THE MOUTH-PARTS OF SOME BEETLE LARYiE. 
393 
tongue of Geotrupes and the maxillulae of Dascillus, and 
evidently represents the left maxillula. It is curious that 
this appendage should have persisted in a vestigial form on 
one side only of the tongue. The spines in a somewhat 
corresponding position on the right-hand side (fig. 27, sp. 1 ) 
resemble in character those below the transverse sclerite on 
the left rather than those of the maxillular lobe opposite, so 
that we are inclined to regard the presence of the latter on 
the right-hand side as exceedingly doubtful. If represented 
at all, it has undergone much more degeneration than on the 
left. The position of the labium with regard to the head- 
skeleton and liypopharynx (Text-fig. 5, a, b) in the Phyllo- 
pertha larva is closely similar to what we have already noted 
in the cases of Dascillus and Geotrupes. 
Conclusion. 
We trust that this brief study has proved the great interest 
which surrounds the tongue and its associated structures in 
the larvae of Coleoptera. We hope that we or others may 
have opportunity for the further pursuit of the inquiry. 
There can be little doubt that the maxillulae — those appen- 
dages so characteristic of the most primitive insects — which we 
find distinctly present in larval Dascillidae, and in a vestigial 
condition in Scarabaeid larvae, will be observed in the larvae 
of beetles of other families. The comparisons of these 
structures in a large series of forms will reveal further stages 
in that process of degeneration which we have shown to be 
illustrated by their successive reduction in Helodes, Dascillus, 
Geotrupes, and Phyllopertlia respectively. 
As we have already pointed out in the Introduction, the 
comparatively full development of the maxillulae. in the 
campodeiform Dascillid larvae, and their reduction to minute 
vestiges in the eruciform Scarabaeid grubs, afford strong- 
support to our belief in the primitive nature of the former 
type. The fact that in these beetle larvae alone among 
metabolic insects have the maxillulae as yet been detected 
suggests that the Coleoptera must be, in many respects at 
