424 EXTERNAL ANATOMY OF INSECTS. 



this takes place, it being very short and wide, and usu- 

 ally terminating towards the tongue in three lobes or 

 teeth which form two sinuses varying in depth a . 



The mentum taken by itself affords no very striking 

 characters to which I need call your attention : I shall 

 only observe, that in Hymenoptera it is generally of a 

 triangular shape b ; but before I proceed to consider the 

 labial palpi, it will be proper to notice the remarkable 

 labium of Orthopterous insects, and of the Libellulina, 

 between which there is no little analogy. At first you 

 would imagine the terminal part of this organ in the for- 

 mer to be the analogue of the tongue, or ligula F. ; as it 

 is indeed generally regarded by modern Entomologists c . 

 It seems, like the tongue of the Carabi L., Dj/tisci, &c, to 

 be a distinct piece, which has below it both labium and 

 mentum; but when you look within the mouth, you will 

 find a linguiform organ d , which evidently acts the part 

 of a tongue, and therefore ought to have the name ; and 

 the piece just alluded to must either be regarded as the 

 termination of the lip, or as an external accompaniment 

 of the tongue, analogous, it may be, to the paraglossce in 

 bees e . In a specimen of Acrida viridissima (Locusta F.) 

 which I dissected, the tongue is as long as the appen- 

 dage of the under-lip, and by its upper surface seems 

 to apply closely to it. In the Libellulina a similar organ 

 is discoverable f , which on its upper-side terminates in 

 the pharynx, like that of one of the Harpalida before 

 mentioned. In the Orthoptera, therefore, I regard the 

 labium as consisting of three articulations, the upper one 



* Plate XXVI. Fig. 24. b'. b Plate VII. Fig. 3. a". 



1 N. Diet. d'Hisf. Nat. xxiv. 171. d Plate VI. Fig. 6. e'. 



2 Plate VII. Fig. 3. i". « Plate VI. Fig. 12. e'. 



