CHAP. CV. _ CORYLA‘CEE. QUE’RCUS. 1823 
insects, chiefly belonging to the order Hemfptera of Linnzeus (Homéptera 
Latr.), and furnished with an elongated rostrum, which they introduce with- 
out difficulty into the soft substance of the young parts, and thereby imbibe a 
sufficient supply of nourishment. Amongst these are to be mentioned, Psylla 
quércus, Eriosoma quércus, A‘phis quércus, and A‘phis réboris. Céccus 
quércus Linn. is a species about the size of a pea, which attaches itself 
to the branches at the base of the young stems. Another insect of the 
same genus, of a species not yet determined, is more injurious, as we learn 
from a communication made by M. Victor Audouin to the Entomological 
Society of France, on the 6th of April last (1836), by whom a portion of the 
bark of an oak, of about thirty years’ growth, was exhibited, entirely covered 
with specimens of a coccus about the size of a pin’s head. These insects were 
of a greenish or orange yellow colour, and were females, destitute of motion, 
adhering to the tree by means of their rostrum, which had pierced the bark. 
The oak had been in a Janguishing state, and was condemned to be cut down 
by the director of the Bois de Bologne, having, as M. V. Audouin judges, 
been brought into this state by the presence of many millions of these insects, 
which covered the entire trunk from 6in. above the ground to the top, 
completely altering the natural colour of the tree, as from 50 to 100 might be 
counted in the space of a square inch. 
The Acorns are devoured by the larve of a small weevil belonging the genus 
Balaninus (B. glandium), and very nearly related to the nut weevil ; as well 
as by the larva of 7'inea Pomonélla (according to Geoffroy). 
Galls. The various parts of the oak are also subject to the attacks of dif- 
ferent species of hymenopterous insects belonging to the Linnzan genus Cy- 
nips (fam. Cynipide Westw.), Diplélepis Ov. and Leach, or gall flies, so named 
from the various excrescences which they produce upon the leaves, stems, &c. ; 
and which are designed by nature to protect the delicate ova and larve of 
certain insects. Entomologists say that the tumours on the leaf stalks, and 
those on the fruit stalks, are produced by different species of Cynipidz ; that 
the galls on the branch are produced by a distinct fly from that which pro- 
duces the gall on the leaf; and it has also been ascertained, that the gall flies 
on the oak leaf are of at least three different kinds. There are also distinct 
kinds of gall flies for the root, bark, bud, and acorn cup, independently of the 
kermes and gall nut. The various species have been named, C. quercis f6lii 
Linn., C.q. baccarum Linn., C. q. inferus Linn., C.q. petioli Linn., C. q. 
ramuli Linn., C. q. cérticis Linn., C. q. gemme Linn., C. q. pediinculi Linn., 
C. q. cdlycis, C. q. terminalis Fab., &c. (See also M. d’Anthoine’s Cynipédo- 
logie du Chéne rouge in the Nouv. Journ. de Physique, t. i. p. 34—39.) 
There is another circumstance, also, connected with this subject, of con- 
siderable interest in a physiological point of view (independently of the man- 
ner in which the gall, consequent upon the puncture of an insect is formed), 
and which is thus alluded to by Dr. Johnston of Berwick :—“ We observe that 
the irritation caused by the deposition and evolution of the egg will produce 
growth of the most curious kind; and differences in the irritation, too slight 
to be traced, will occasion very remarkable differences in the appearance of 
the growth. Thus, in the oak leaf, one insect irritation produces a globular 
smooth ball; and another, a depressed tumour, covered with a hairy scarlet 
coat. The first is seated on the substance of the leaf, and cannot be removed 
without destroying the texture of the part; the other seems almost placed on 
the leaf, and can be detached with facility. Examples equally remarkable 
will occur to every one who has paid any attention to this curious subject ; 
and the growths appear to be not less uniform, and not less organised, than 
many parasitical fungi.” (Flora of Berwick upon Tweed, vol.ii. p. 108.) 
The British oak does not bear a gall nut of such powerful qualities as that 
of Q. infectdria ; but, like the galls of commerce, those British galls are said to 
be the best from which the insect has not escaped. The largest species of 
British galls is generally called the oak apple, or oak sponge (Spongia quércina 
of the ancients), These are produced by C. q. terminalis Fab. (Réaum. 
6c 
