on_, rather than _in_, the head,
because it is formed by a modification of part of the antennae. A German
naturalist, named Mayer, performed an experiment to prove that the hairs
on these antennae can be made to vibrate by means of a tuning-fork. Only
those hairs which have to do with the production of sound answered to
the notes of the tuning-fork, and these vibrated at the rate of five
hundred and twelve vibrations per second. Other hairs vibrated to other
notes, which were those of the middle octave of the piano and the next
above it. Mayer also found that certain of these vibrations corresponded
with the notes produced by the 'song' of the female mosquito.
Consequently, when she begins to 'sing,' her tune, like the tuning-fork,
sets in motion those hairs on the antennae of the male which are tuned to
these vibrations. Having once found, by the movement of his antennae,
much as a horse moves his ears, from which direction the sound is
coming, the male is able to fly at once to his mate. From the accuracy
of this flight, Professor Mayer believes that the perception of sound in
these little creatures is more highly developed than in any other class
of animals.

[Illustration: Fig. 1.--Grasshopper, slightly magnified.]

In our illustration some of these curious 'ears' are shown. Fig. 2 shows
the ear of the grasshopper magnified. In fig. 3 this is further
magnified to show the V-shaped mark which represents the horny stalks to
which we referred, seen through the clear membrane of the drum. The dark
border (B) around the drum represents a raised ridge. In fig. 4 we have
the antennae of a gnat, some of the hairs of which serve as
sound-conductors to delicate nerves lying at their base.

[Illustration: Fig. 2.--Ear of Grasshopper, drum at A, greatly
magnified.]

[Illustration: Fig. 3.--Drum of Grasshopper's Ear, greatly magnified.]

* * * * *

The sense of smell in insects lies mainly in those wonderful organs, the
antennae or 'horns.' Scents of various kinds are perceived either through
pits, or through peg- or spike-like teeth filled with fluid. The
leaf-like plates of the antennae of the cockchafer (fig. 5) have these
pits very highly developed. On the outer surface of the first 'antennal'
leaf, as also on the edges of the other leaves, only scattered bristles
are seen; but on the inner surface of the first and seventh leaves, and
on both surfaces of all the other leaves, there are cl