EXTERNAL ANATOMY OF INSECTS. 421 
patiently investigated, it will be found that on their 
upper side its roots are attached to the interior of the 
upper side of the head, as well as on their lower side to 
the Jabium ; so that it may be regarded as common to 
the two lips, and therefore not properly considered as 
an appendage of the under-lip alone. 
Having assigned my reasons for preferring the name 
given to the part in question by Fabricius, rather than 
that of Latreille, I shall next make my observations on 
the part itself. In many cases the labium, or the middle 
piece of the lower oral apparatus, appears to consist of 
two joints: this you may see in the great water-beetle 
(Hydrophilus piceus), the burying-beetles (Necrophorus), 
the Orthopterous tribes *, the Hymenoptera», and others. 
In this case the upper or terminal piece is to be regarded 
as the Jabium, and the lower or basal one (which Mr. 
MacLeay calls the stipes) as the mentum or chin—at 
other times, as in some Lamellicorn beetles, the only se- 
paration is a transverse elevated line, or an obtuse angle 
formed by the meeting of the two parts, and very fre- 
quently there is no separation at all, in which case the 
whole piece, the mentum merging in it, may be denomi- 
nated the labium. 
With respect to its substance, the labium in most Co- 
leopterous insects is hard and horny, in Necrophorus it 
is membranous, and the mentum harder; in Prionus 
coriarius, our largest Capricorn beetle, both are mem- 
branous; in the bee-tribes, Apis L., the labium rather 
resembles leather, while the mentum is hard. Its surface 
is often convex, sometimes plane, and sometimes even 
concave; as for instance in Melolontha Fullo, a rare 
* Prarte VI, Fie. 6. b!. a". b Prate VII. Fre..3. b!. al’. 
