EXTERNAL ANATOMY OF INSECTS. 423 



concave; as for instance in Melolontha Fullo, a rare 

 chafer occasionally found on the coast of Kent. In some 

 it is covered with excavated points ; in others it is quite 

 smooth. In numbers, as in the Predaceous beetles, both 

 labium and mentum are perfectly naked ; in others, as in 

 the common cockchafer, they are hairy ; in Geniates bar- 

 batus Kirby, another chafer in the male insect, the la- 

 bium is naked, while the mentum, which forms a piece 

 distinct from that part, is covered with a dense rigid 

 beard a . In shape the whole labium varies considerably, 

 much more than the labrum ,• for in addition to most of 

 the forms I enumerated when I described that organ, 

 which I shall not here repeat, you may meet with exam- 

 ples of many others. Thus, to instance in the Petalocerous 

 tribes (Scarabams L.), in some, as in the Rutelidce, the 

 labium is urceolate, or representing in some degree the 

 shape of a pitcher b ; in others it is deeply concave, and 

 not a little resembles a basin or a bowl c ; this form is 

 peculiar to the labium of Cremastocheilus Knoch, a scarce 

 North American beetle ; in another related to this, but 

 of an African type (Genuchus, Kirby MS. Cetonia cru~ 

 enta F.) 3 it is a trapezoid plate, which is elevated from 

 the head, and hangs over the throat like a chin d . In the 

 Hymeyiojptera it is extremely narrow and long, and em- 

 braces the sides of the tongue, as well as covering it from 

 below; so that it wears the appearance of a kind of tube e . 

 Generally speaking, the length of the labium exceeds its 

 breadth ; but in the Predaceous beetles the reverse of 



a Kirby Linn. Trans, xii. t. xxi./. 8./. 



b Ibid. t. xxi./. 10. d. MacLeay Hor, Entomol. i. t. m.f. 26, 27. 

 c Plate XXVI. Fig. 35. d Ibid. Fig. 34. 



f Plate VII. Fig. 3. b'. 



