416 EXTERNAL ANATOMY OF INSECTS. 
which, to avoid circumlocution, instead of Jnstrumenta 
cibaria, the name Fabricius gave them, I shall call Trophi 
or feeders. It is upon these parts, you are aware, that 
the system of the celebrated Entomologist just mentioned 
is founded; and could they always, or even for the most 
part, be inspected with ease, they would no doubt afford 
characters as various and discriminative as those of the 
vertebrate animals. Differences in these parts indicate 
a difference in the mode in which the animal takes its 
food, and often in the kind of food and sometimes in its 
general economy and habits,—circumstances which are 
powerful and weighty in supporting the claim of any set 
of animals to be considered as forming a natural genus 
or group. ‘Trifling variations, however, of these parts, 
unless supported by other characters and qualities, ought 
not to have much stress laid upon them, since, if we in- 
sist upon these, in some tribes almost every species might 
be made a genus. 
With respect to their Tropfz in general, insects of late 
have been divided into two great tribes*, masticators and 
suckers ; the first including those that are furnished with 
instruments to separate and masticate their food; namely, 
an upper- and under-lip (dabrum and labium), upper- and 
under-jaws (mandibule and mazille), labial and maxil- 
lary palpi, and a tongue (/ingua): and the second those 
in which these parts are replaced by an articulate or ex- 
articulate machine, consisting of several parts and pieces 
analogous to the above, which pierce the food of the ani- 
mal, and form a tube by which it sucks its juices. If, 
however, the mode in which insects take their food be 
* Clairville (Ent. Helvet.i.44) appears to have been the first who 
classed insects according to their mode of taking their food, 
