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PROCEEDINGS OF THE PERTHSHIRE SOCIETY OF NATURAE SCIENCE. 
respect, though still retaining the essential characters of 
structure of the Cynipid®. 
The true gall-makers are found on both the European 
and the North-American sides of the Atlantic, though as 
yet apparently more abundant in Europe than in America. 
Probably this is due in great measure to the larger number 
of entomologists and botanists in Europe by whom these 
curious structures have been studied. To an American 
entomologist is due the credit of having been the first to 
discover the existence of “dimorphism” in any insect of 
the Cynipidae ; Mr B. Walsh having published in 1870 
(American Entomologist, vol. ii., p. 330), a paper describing 
the life-history, as deduced from his own observations, of 
the supposed species Gy nips aciculata o.s. and C. spongifica; 
and showing that there was reason to regard them as merely 
generations in the development of a single species. Little 
need was paid to this discovery for several years, as it 
stood as an isolated, and therefore distrusted, statement. 
In 1877 Dr Adler first published a brief announcement of 
the results of carefully-conducted experiments and obser¬ 
vations made by himself on several different species of 
European Cynipidae ; announcing that in a number of the 
Gall-makers on Oaks, in each species there are two quite 
distinct forms, giving origin to two usually very different 
forms of galls ; that the forms are exclusively confined to 
different periods of the year in their development; and 
that the insects of the two broods are often so distinct from 
one another in appearance, and even in structural charac¬ 
ters, that they have been described as distinct from one 
another, not only specifically but even generically. He 
published not long afterwards the results of longer con¬ 
tinued labours in the same line, and as the result of these 
he asserted that a number of the so-called species of pre¬ 
ceding systematic writers are simply stages in the full 
cycle of development of other species earlier described and 
named as distinct. In this way the number of species 
would have to be considerably reduced, but, as already 
stated, difficulties in the life-history of not a few species 
have been cleared away by the new views put forward by 
him. Of course, Dr Adler's announcements were at first 
received with hesitation, so novel were they; nor is there 
good cause for anything like complaint that revolutionary 
ideas should make their way with some difficulty, and that 
they should be well sifted before they are generally accepted 
as received truths. But while it is well that due caution 
should be exercised in their reception by those to whom 
they are presented for the first time, and who have not had 
the opportunity to verify them for themselves, so much the 
greater honour must we ascribe to him, who, in the face 
of distrust and opposition, proves his accuracy and wins 
general recognition of the value and trustworthiness of his 
discoveries. This Dr Adler may be said to have fully suc¬ 
ceeded in effecting. 
It is a noteworthy and rather curious fact that dimor¬ 
phous Cynipidae are known as yet only among the gall- 
makers that live on the Oaks (with the exception of one 
on Maples); but even among them this peculiarity is by 
no means universally met with. 
It may be well, before entering into details of the life- 
history, as traced by Dr Adler, of any of our native Cyni¬ 
pidae, to dwell a little on what was known previous to 1870 
about the life-history of these insects, and of the course of 
development of their galls, as the problems in connection 
with their development will be thereby seen more clearly 
as they presented themselves to inquirers of that period, 
and the advance made by Mr Walsh and Dr Adler will be 
better appreciated. 
In what I may have to say in respect to the Cynipid®, 
I shall confine my remarks exclusively to those that cause 
the numerous galls on oaks, and shall as far as possible 
refer to common and widely-known Scottish galls and 
their makers. I shall also have to indicate the results of 
the new views as relating to our Scottish oak-galls, and to 
point out what forms we may look for that have not been 
recorded for Scotland, but that must occur with us, if Dr 
Adler’s identifications of the two forms are correct in all 
cases. Several galls are known from Scottish localities, 
the corresponding forms to which, i.e., the second genera¬ 
tion, have not yet been found here; hence it is of interest 
to attend specially to such forms, alike because they are 
definite objects to be sought out, rendering more complete 
our knowledge of our native fauna, and because if, after 
careful search, they cannot be found here, their absence 
may enable us to correct errors in detail in the identifica¬ 
tions that have been determined or suggested in the group; 
and correction of errors is of no less value than actual 
advance and addition to our knowledge. 
Even the least observant must be quite familiar with 
several of the numerous very different galls that are fre¬ 
quently so abundant on our native oak-trees; and pro¬ 
bably the question has suggested itself to almost every 
non-scientific, as well as to every scientific observer, what 
could be the cause of their production. There are pro¬ 
bably few persons now-a-days that are not aware that 
insects have to do with their production, in some ill-under¬ 
stood manner; but probably most non-entomological 
inquirers have rather a vague idea of the appearance of 
the insects themselves, though the desire of knowledge 
may have led them so far as to have cut open galls, and 
have so familiarised them with the fact of a small pale- 
