LOWER LIP. 259 



angular piece, which appears analogous to the part which 

 I have noticed above, as the stipes of MacLeay, although 

 here, for evident purposes, it is articulated and moveable. 

 The next piece is the thickened horny tubular piece, or 

 mentum, at the extremity of which arise the labial palpi, re- 

 markable for the elongation of the two basal joints, and be- 

 tween which, at the base, are two short processes, which are 

 termed paraglossae ; the apparatus terminating in a long and 

 slender many-ringed instrument, which, in a following page, 

 I have called the tongue, or lingua, but its true analogy 

 has not been determined. By some authors it is called the 

 labium. 



In the lepidopterous insects, the structure of the mouth, 

 although having a function similar to that of the bee's, is 

 completely altered as to the form of its individual organs. 

 In the latter, the maxillae and labium conjointly operate in 

 sucking up honey; but in the former (see fig. 87), the 

 maxillae (m x) alone perform this office, the labium (I 2) 

 being rudimental, and attached to the head, and only distin- 

 guishable by bearing the pair of large palpi (I p), which bend 

 upwards, and form the defence of the spiral maxillae. In the 

 Diptera (see fig. 88), on the contrary, as well as the Hemi- 

 ptera (see fig. 89), the labium (I 2) is the most conspicuous 

 part of the mouth, forming the elbowed and fleshy, or arti- 

 culated and membranous, tube or canal, in which the other 

 organs of the mouth are inclosed. In these orders, more- 

 over, the labial palpi are obsolete : great variations occur in 

 these orders, and especially in the Diptera, as regards the 

 form of this lower lip ; but it would lead to too great a 

 length were I to notice them more in detail. The forest 

 flies, Hippoboscidce, and the flea, exhibit other modifications 

 of form of the lower lip. 



Such are the various and important head-organs with 

 which Nature has supplied insects for the due support of 



