INSECTS : THEIR MOUTHS. 141 



beetle has three pairs of these many-jointed organs, viz., 

 the labial, and the two pairs of maxillary palpi. 



Now, in this form of mouth, which has been called a 

 perfect or complete mouth, — that is, one in which all the 

 constituent parts can be well made out, we find the fol- 

 lowing organs : — 1. the upper lip (labrum) ; 2. the man- 

 dibles; 3. the maxilla?; with o, the maxillary palpi; 4. 

 the lower lip (labium), comprising /3, the tongue, y, the 

 labial palpi, c, the chin (mentum). 



I now exhibit to you the head of the Honey-bee. The 

 front is occupied by an upper lip, and a pair of biting 

 jaws (mandibles), which do not greatly differ from the 

 same parts in a beetle. The jaws, however, are more 

 hatchet-shaped, or rather like the hoof of a horse, sup- 

 posing the soles to be the opposing surfaces. The other 

 organs are greatly modified, so that you would scarcely 

 recognise them. The under jaws (maxillce) are greatly 

 lengthened ; and the two, when placed in contact, form a 

 kind of imperfect tube or sheath. Within these is the 

 lower lip, divided into its constituent parts : the thick 

 opaque chin, at its basal end ; then the two labial palpi, 

 each consisting of four joints, of which the two terminal 

 ones are minute, while the two basal are large and 

 greatly lengthened, so as to resemble in appearance the 

 maxillce, whose function they imitate also ; for the pair 

 of palpi when closed form an inner sheath for the tongue. 

 Finally, you see this organ, which is the most curiously 

 developed and modified of all, for it is drawn out to a 

 long slender, cylindrical tube, formed of a multitude of 

 close-set rings, and covered with fine hairs. Some deny 

 it to be tubular, and maintain that it is solid ; but cer- 

 tainly it appears to me to have a distinct cavity through- 

 out, with thickish walls. 



Under a high power the structure of the investing hairs 

 is very interesting ; for they are seen to be flat filaments 

 of the yellow chitine, very much dilated at their bases, 



