104 INTRODUCTION TO 



figure and proportion of the joints are very variable ; 

 the terminal joint especially exhibits a great variety 

 of forms, which are of great service in distinguishing 

 genera. The number of joints never exceeds six. 



Closing the mouth on the underside is a piece 

 which acts as an antagonist to the upper lip, and 

 has therefore been named the under lip or labium. 

 The basal portion of this constitutes the mentum or 

 chin ; which is a quadrangular, trapezoidal or semi- 

 circular plate. The part immediately adjoining this 

 and anterior to it, is the labium properly so called, 

 usually bearing the labial palpi. The terminal por- 

 tion is the ligula or limb, frequently divided into lobes. 

 The labial palpi are similar in structure to the max- 

 illary pair, but they always consist of a smaller 

 number of joints, the greatest amount never exceed- 

 ing four. 



The tongue (lingua) is usually a very obscure 

 member of the trophi, and authors do not always 

 assign that name to the same organ. It may be 

 described as the lining membrane of the under lip, 

 the anterior angles of which sometimes protrude in 

 front, as may be seen among the Carabidce, a tribe 

 in which the projecting points have been named 

 paraglossee. It is most distinct among the orthoptera. 



On examining a mouth formed for suction, it ap- 

 pears, at first sight, to be constructed on such a dif- 

 ferent model from that just described, that it seems 

 almost a hopeless case to attempt to trace any analogy 

 between the parts. But it is not long before we 

 can discover an essential agreement, although the 



