418 EXTERNAL ANATOMY OF INSECTS. 



strictly considered, it will be found that in this view they 

 ought rather to be regarded as forming three tribes ; for 

 the great majority of the Hymenoptera order, and per- 

 haps some others, though furnished with mandibles and 

 maxilla?, never use them for mastication, but really lap 

 their food with their tongue : these, therefore, might be 

 denominated lappets. 



When a mouth is furnished with the seven ordinary 

 organs used in taking the food and preparing it for de- 

 glutition — I mean the upper-lip and the two upper-jaws ; 

 the under-lip and the two under-jaws, including the la- 

 bial and maxillary palpi; and the tongue — I denominate 

 it a perfect mouth ,- but when it is deficient in any of these 

 organs, or they exist merely as rudiments, or when their 

 place is supplied by others, (which, though they may be 

 analogous parts, have little or no connection with them 

 in their use or structure,) I denominate it an imperfect 

 mouth. This last I would further distinguish, according 

 to the nature of its trophi, by other and more distinctive 

 terms, as I shall presently explain to you. 



1. Labrum*. — I shall first consider the organs pre- 

 sent in a perfect mouth, beginning with the upper-lip [la- 

 bruin). This part, which Fabricius sometimes confound- 

 ed with the nose, miscalling it clypeus, is usually a move- 

 able b piece, attached by its base to the anterior margin 

 of the part last named, and covering the mouth, and 

 sometimes the mandibles, from above. In insects in 

 their last state it is usually of a horny or shelly substance; 

 yet in some cases, as in Copris and Cetonia, beetles that 



a Plate VI. VII. XXVI, a'. 



b In Luc-anus, Lamprina, &c. the labrum seems to form the under- 

 side of the nose, and to be connate with it. 



