422 EXTERNAL ANATOMY OF INSECTS. 



ter is thoroughly and patiently investigated, it w ill 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 labium ,• so that it may be regarded as 

 common to the two lips, and therefore not properly con- 

 sidered 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 oi 

 two joints : this you may see in the great water-beetle 

 (Ut/drojjkilus piceus), the burying-beetles (Necrojjhorus), 

 the Orthopterous tribes a , the Hymenoptera b , and others. 

 In this case the upper or terminal piece is to be regarded 

 as the labium, and the lower or basal one (which Mr. 

 MacLeay calls the stipes) as the mention 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 



» Plate VI. Fig. G. b'. a". * PlatS: VII. Fig. 3. b'. a'. 



