MANUFACTURE OF NUT GALLS BY THE GALL INSECT.
“No present that insects have made to the arts is equal in utility and
universal interest, comes more home to our best affections, or is the
instrument of producing more valuable fruits of human wisdom and genius,
than the gall insect: I mean the fly that gives birth to the gall-nut,
from which ink is made. How infinitely are we indebted to this little
creature, which at once enables us to converse with our absent friends
and connexions, be their distance from us ever so great, and supplies
the means by which, to use the poet’s language, we can
“——give to airy nothing
A local habitation, and a name!”
enabling the poet, the philosopher, and the divine, to embody their
thoughts for the amusement, instruction, direction, and reformation of
mankind.”[3]
Footnote 3:
Kirby and Spence.
The oak which furnishes this gall is common throughout Asia Minor, from
the Bosphorus to Syria, and from the shores of the Archipelago to
Persia. It is more frequently seen under the form of a shrub than a
tree, rarely attaining six feet in height. Its leaves are smooth,
toothed at the edges, of a clear green on both sides, and having a very
short leaf-stalk; they fall every year, at the end of autumn. The acorn
is two or three times longer than its cup, the latter is sessile,
slightly downy, and furnished with small scales. The gall is hard,
woody, and heavy, growing out of the buds of young branches, and
acquiring a diameter of from four lines to an inch. It is generally
round, and covered with knots, some of which are pointed.
This gall-nut is much more valuable if gathered before it is ripe, that
is to say, before the insect which produced it has made its escape. In
this state it has a bluish appearance, and is unperforated; whereas
those from which the insect has departed are lighter in colour and in
weight, and are less useful in dyeing.
The Orientals are very careful to gather in this crop at the exact time
which experience has proved to be the best, namely, that in which the
excrescence has attained its greatest size and weight. If there is any
delay, the insect undergoes its metamorphosis, pierces the shell, and
appears under its form of a winged insect. From this time the gall-nut
no longer derives from the tree those juices which were necessary for
the nourishment of the insect, but dries up, and loses the greater part
of those qualities which make it valuable in commerce. The Aga of the
district takes care that the cultivators traverse frequently, at the
time of the harvest, the hills and mountains which are covered with this
oak. He has an interest in obtaining galls of good quality, because he
levies a tax on the produce. The first gatherings are set aside; they
are known in the East under the name of _yerli_, and are called in
commerce _black galls_, and _green galls_. Those which have escaped the
first search, and which are gathered a little later, are named _white
galls_, and are of a very inferior quality.
The galls from Mossoul and Tocat, and in general those which come from
the eastern part of Turkey, are less valued than those from the
neighbourhood of Aleppo, of Smyrna, Magnesia, Diarbekir, and all the
interior of Natolia.
The acorns of this oak are nearly always neglected; being left as
pasturage for goats and wild boars: this it is thought contributes much
to render the oak small and stunted, because in devouring the fruit,
these animals also consume a part of its foliage and young branches.
The body of the insect which produces the gall-nut, is of a fawn colour,
with obscure antennæ; the abdomen is shining brown. It is sometimes
found in its perfect form in the interior of the nut.
On the same oak are frequently found a great number of other galls,
which are not gathered, because they are of no use in dyeing. One of
these is represented in the frontispiece to this chapter, and is
remarkable for its large size. It is spongy, very light, of a reddish
brown colour, and covered with a resinous matter. It is also furnished
with a circular range of tubercles, placed near its greatest
circumference. This is produced by a different insect, called by Olivier
_Diplolepis gallæ resinosæ_; a figure of which is also given on the
right hand side.
Gall-flies of various kinds attack our oak trees in this country, and
also our willows, hawthorns, roses, &c. A few words respecting the
excrescences they produce, may therefore assist our ideas of the
proceedings of the valuable insect described above. Very few persons are
unacquainted with oak-apples, or small roundish, flattened bodies
growing on the leaves of the oak. These are sometimes tinged with brown,
or pink, or pale yellow, so as to appear not much unlike very small
apples, attached to the leaf. Each of these curious bodies is formed by
a small fly of the same nature as that which forms the gall-nut. This
insect alights on the leaf, pierces it with a very sharp instrument with
which she is provided for this purpose, and deposits an egg so minute as
to be almost invisible to the human eye. The puncture of this insect
produces a diseased action in the leaf, so that the parts immediately
surrounding the egg swell and harden until the apple-shaped body is
produced. This is now an admirable place of shelter, and a reservoir of
food for the insect within, which remains snugly encased until it
arrives at its perfect state, when it cuts its way out through the solid
substance of the gall.
[Illustration:
LEAF GALLS.
]
[Illustration:
OAK SPANGLE.
]
This is only one out of many forms of gall that may be found on the oak,
where sometimes the leaf is attached, sometimes the catkin, and
sometimes the young bud. Another form of that on the leaf consists of
very small circular discs fixed to the under part by their central
points. The outer side of the disc is red and hairy, the inner side
smooth. Each disc contains a single insect, which remains in it long
after the leaves have fallen to the ground. The common name of this
curious excrescence is “oak spangle.”
[Illustration:
CURRANT GALLS.
]
Still more singular is the gall found in the catkins of the oak. The
flies deposit their eggs in the stalk of the stamen-bearing flowers,
which in consequence become adorned with what appear to be straggling
bunches of currants or bird-cherries. Placed at short distances from
each other on the thread-like stem, these excrescences so much resemble
currants in size, shape, and mode of growth, that they have been named
“currant galls.”
[Illustration:
ARTICHOKE-GALL.
]
Among the species of gall to which our oaks are subject, there are some
which grow at the end of the twig, as for instance, that called the
artichoke-gall, which comes the nearest in appearance to the nut-gall of
commerce, since it is, in common with that nut, an irregular
development, not of the leaf or flower, but of the bud. The
artichoke-gall might indeed be easily mistaken for the fruit of the
tree, by any one unacquainted with the habit of the oak. It is a
cone-like body, consisting of a number of leafy scales overlapping each
other, but on being dissected it is found, like other galls, to contain
insects in various stages of their growth, according to the season. In
the same way, the nut-gall, being a disease of the bud, or extremity of
the young shoots of the oak on which it grows, has the appearance common
to some other kinds of fruit, and would seem to be the ordinary produce
of the stalk, did we not find that acorns also grow on the same tree.
The hard and brittle texture of the gall-nut also, so different from the
substance of our own oak-galls, would be still more likely to deceive,
and indeed has deceived a highly respectable writer, who declares from
his observation of the dried galls of commerce, that the nut is the
fruit of a tree, and not a mere excrescence.[4]
Footnote 4:
Aikin.
How it is that the different species of gall-fly should produce such
varied results, and why one excrescence should be the oak-apple, another
the spangle, a third the artichoke, and a fourth the nut, is indeed a
mystery. But that these small insects do really produce the excrescences
in question, is an ascertained fact, and a most important one in the
commercial world.
Nut galls contain a large quantity of the vegetable principle called
_tannin_, being the astringent property for which oak-bark is in so much
repute. They also abound in an acid called from thence _gallic acid_,
which is the important ingredient in black dyes, and in fixing and
improving several other colours, as well as in the composition of ink.
[Illustration:
BLISTERING BEETLE.
]