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 
paraglossse. 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 
