284 OAK GALLS AND GALL INSECTS
to escape and the necessary investigations can be carried on
without difficulty. As the oak does not usually bear fruit until
it is about twenty years old (though it depends to a large extent
upon soil and climate), this method is obviously useless in the
cases of those species which produces galls on the catkins. For
these the only way is to experiment upon the full grown tree by
covering in certain branches with gauzs. When the act of
oviposition is witnessed the bud or leaf should be marked by
tying just beneath it round the branch, a piece of cotton or wool.
It is necessary with those galls which fall to the ground to
mature (such as Neuroterus lenticularis) that the natural temperature
and amount of moisture should be maintained. As before men-
tioned, in order to prevent any mistakes, it is desirable that very
careful and accurate observations should be made. It is always
best when possible that a series of different experiments with the
same species should be carried on at the same time. Where
one experiment fails another may be successful, and time
saved. Even then many disappointments are sure to occurs
The result of one apparently successful experiment in breeding
should not be taken as proof, but to allow for possible error
the observation should be repeated the following year. There is a
great deal yet to be found out with regard to alternation of
generations among these remarkable insects, and in the case
of such species as Andricus solitarius the life-history has yet to be
worked out.
Preservation of Galls.
With regard to the preservation of galls for a collection.
There are many kinds which are very difficult to preserve as
they lose their colour and shrink ; and this especially applies
in the case of such galls as Andricus radicis which contain a
great amount of moisture, causing the gall to shrivel and wrinkle
after evaporation. I have tried the quick drying method with
only partial success, and in many instances by gradual drying
and by not exposing the galls to any very high temperature I
have caused them to keep their shape and colour fairly well;
but such galls as Neuroterus tricolor and N. baccarum soon lose
both. If kept in spirit the proper form is retained but the colour
as a rule gradually vanishes. I find that the best thing to do
is to make coloured drawings of the galls when fresh, so that a
fair idea of their natural appearance may be had, after the
galls themselves have lost their proper shape and colour.