The tettix or cicada,

alone of such creatures (and, in fact, alone
of all creatures), is unprovided with a mouth, but it is provided with
the tongue-like formation found in insects furnished with frontward
stings; and this formation in the cicada is long, continuous, and
devoid of any split; and by the aid of this the creature feeds on dew,
and on dew only, and in its stomach no excretion is ever found. Of the
cicada there are several kinds, and they differ from one another in
relative magnitude, and in this respect that the achetes or chirper is
provided with a cleft or aperture under the hypozoma and has in it a
membrane quite discernible, whilst the membrane is indiscernible in
the tettigonia.