The San Francisco call., 1899-07-09
GALL INSECTS.
How They Make Material for Various
Inks and DYES


| Oak apples. so called. are familiar OBJ
Jects to almost every one, yet few under
stand their real nature. Many persons
suppose them to be sort of fruity growth
of the tree on which they are found. Be
sides the oak apples there are similar
sWellingS and fruitlike grOWthS, some of
which are attached to tWigs and are no
larger than cherries, while others grow
on leaves and are as large as hens egg,
hut OF more globular form. Some are
hard within, some soft but woody in tex
ture; others are pithy or spOngy, and still
others are nearly hollow, with strings or
hbers radiating from the center.
All kinds have in the middle a small.
hollow, pea-shaped or seedlke cell, which
contains the. insect that is the real cause
of the growth. The irritation to the leaves
or twigs caused by these tiny insects
| gives these abnormal growths the distinc-
tive and appropriate name of gals" by
which they have long been known.
Gall flies are among the most peculiar
of all the insect tribes. They belong to
flies, but they never sting or harm men
or animals. The female gall fly. fmpelled
safety and welfare of her offspring cuts
away the outer skin or bark of a leaf or
twig and deposits therein an egg; From
| this is hatChed a small white grub, with
mouth. AS it eats its way into the sur
rounding tissue the plant Is seemingly in
| V1gorated, and begins to enlarge about the
tiny larvae and grow into a shape well
suited to its needs as a place of conceal
ment I1 and food supply. While all flies Of
exactly alike. every species produces
different form. Exactly why this is so has
never been explained, yet we see parallel
| instances everywhere in nature.
| When the larva is full grown 1t is trans
| formed in its narrow cell to a rey-eyed,
| whitish pupa, helpless and almost motion
less. yet having rudimentary antennae,
legs and wings, which give promise of the
coming gail fly. This. in many species. is
| a gayIy cOlOred insect, with red eyes.
more or less veined wings, a bumped back
| and an exceedingly long oVipOSitOr Thus
| equipped IT emerges from IT'S confinement
and flies abroad, soon to deposit it's eggs
| in leaves and twigs and thus to cause
| other gals.
Yet, strange to say, the successive gen.
! erations of the same species differ widely
! in appearance and even in color. From
gals made by eae spring brood are
| hatched flies of the summer brood, whose
| grubs winter in the gals and produce the
| brood of the following spring. Not only
! do these successive generations differ in
appearance, but the summer brood con-
sfsts of both sexes while the spring brood
| is of females only. In some species one
brood is entirely black. while the follow
| ing one is highly colored.
The blackberry has a gall fly which
! gives exclusive attention to that plant,
and causes a hard swelling. of the stems
filled with several cells each occupied by
a grub. I think the Eight O'Clockers
would find it interesting to gather some
of these curious gals, selecting. those that
they have attained full growth. If they
are put into a receptacle that will admit
little light and air, but will not allow
the gall fly to escape, the process of
Matching out may be observed after
which the prisoner may be liberated. The
flies are often beautifully eolored, some
with red and black bodies, others with
| metallic green or blue reflections.
Oak gals are either spongy or woody,
| The former are of no value to man, but
/ the latter are largely used in the manu-
facture of inks and dyes. This is due TO
the fact that they contain a large per
! centage of tannic acid, and when com
| bined with certain salts of iron form
black, dark brown, or purple dyes, of alb
| solutely permanent color. In our coun-
| try gals adapted to commercial purposes
cannot be found in sufficient quantities to
supply the demand. The gals exported
| from Aleppo, in Syria, are the most val
liable known for the manufacture of inks
and dyes. Ink used for important legal
Eneland and France. to be made from m
gals, such ink having proved to be prac-
tically indelible-Philadelph Times.