102 
INTRODUCTION TO 
lation to tHe insect’s economy, or the uses that have 
been made of them by naturalists in their systematic 
arrangements of the class. 
When a mouth organised for mastication is viewed 
from above, the first part that meets the eye is the 
labrum or upper lip. It is a corneous plate, of 
very variable form, united posteriorly by a mem- 
branous hingo to the clypeus, with which many 
authors, and among others Fabricius, have con- 
founded it. It covers the mouth above, and assists 
in retaining the food while undergoing the pro- 
cess of mastication by the mandibles . The last 
named organs, otherwise called the upper-jaws, are 
two strong, triangular, wedge-shaped, or elongated 
pieces, placed immediately below the labrum, arti- 
culating with the head by means of apophyses or 
processes, and moving horizontally in opposition to 
each other like the blades of scissors. When of a 
horny substance, which is usually the case, they are 
commonly dentate on their inner edge, but the den- 
ticulations are seldom or never alike in both blades, 
but so arranged that the projections of the one enter 
the notches of the other, thus admitting of a close 
union. The maxillce , o r feeler-jaws, as they have 
not inappropriately been called, are placed below' the 
mandibles, and correspond to them in being two tri- 
angular hooks, moving horizontally in opposition to 
each other. They are always smaller than the man- 
dibles, usually of a more delicate texture, and instead 
of being toothed on their internal edge, are* for the 
most part fringed with hairs or bristles. They may 
