376 GEORGE H. CARPENTER AND MABEL C. MACDOWELL. 
the base of the hypopharynx lies within and in front of that 
sclerite. Nevertheless the tip of the hypopharynx in all 
these larvae is fused with the distal extremity of the labium. 
Besides these features of morphological importance, a 
curious asymmetry of the labium of the Dascillus larva 
attracted our attention. Teeth on the ventral, inner face of 
the labrum (PI. 36, fig. 19, t, t z , l) appear to work together 
with similar structures on the hypopharynx (figs. 20, 21, 
t' , t " ,) and maxillulae, but the labral teeth are asymme- 
trically arranged. Believing that this condition might have 
some correlation with the root-feeding habit of the Dascillus 
larva, we have made a comparative study of the correspond- 
ing parts in the larva of Phyllopertha horticola, the 
well-known Garden Chafer, and have found a somewhat 
similar asymmetrical arrangement of the teeth on the labrum 
(PI. 37, fig. 25). In the dung-feeding larva of the Dor-beetle 
(Geotrupes), which we have also examined (PI. 37, figs. 23, 24), 
a less well-marked asymmetry is observable in the labrum, 
while the hypopharynx is strongly one-sided. 
In both Phyllopertha and Geotrupes — belonging as is well 
known to the Scarabaeidae, and exhibiting larval types more 
specialised in nature than those of the Dascillidae — the 
maxillulae are almost merged in the hypopharynx, but are, 
we believe, recognisable on comparison with the correspond- 
ing structures in the Dascillid larvae. 
We proceed now to a detailed description of the mouth- 
parts of these various larvae. 
The Larva of Helodes minuta. 
The specimens examined were found under stones in the 
Glendhu River, near Dublin, in February, 1911. They are 
rather inconspicuous little creatures, and require some search- 
ing for; nor are they as abundant as the larvae of the May- 
and caddis-flies, which share their haunts. 
In general appearance the larva somewhat resembles a 
small woodlouse, the very broad head region accentuating the 
