1826

ARBORETUM AND FRUTICETUM.

PART 1IJ.

winged state, ready to take advantage of the first warm day to burst forthfrom their prison. This gall, which is the largest excrescence that we havehitherto seen formed by any cynipideous insect, is irregularly oblong, and nearly5 in. in length : it is 1 ’ in. in diameter in the thickest part, the general thicknessbeing about 1 in.: its appearance is that of a piece of very fine-grained sponge.On making a section ljtn. long by 1 in. broad, between 60 and 70 cells,closely packed together, and of an oval form, were discovered, each containinga single cynips. Taking the size of the entire gall into consideration, itmust contain, at thelowest calculation, upwards of a thousand individuals, theproduce, probably, of a single female cynips. The perfect insect is of a palebrownish colour, with a shining red abdomen, having two small dorsal black spotsat the base. This gall was unknown to Reaumur, having been first described andfigured by Bose. (Journ. de Physique, 1794-.) A figure, apparently of the samegall, is given in the Insect Architect., p. 385.; but it is there erroneouslystated that the inhabitant is identical with the cynips of the oak apple (C.quercus terminalis) ; and this is supposed to be accounted for by the observa-tion, that the root galls are “ probably formed at a season when the flyperceives, instinctively, that the buds of the young branches are unfit for thepurpose of nidification.” Numerous other excrescences, and some mostcurious distortions, seem to be the result of the attacks of insects on thebuds or branches of the oak in their embryo or infant state, of which thecoadunate stems and witch knots are among the most remarkable; but it isdoubtful whether many of these monstrosities are not idiopathic diseases ofthe tree.

The oak leaves, also, are occasionally observed covered with numerousgalls of small size, and evidently belonging to different species, being of dif-ferent forms, of some of which the insect has notyet been discovered. Several of them are figuredby Reaumur. ( Memoires , tom. iii. pi. 35. fig, 3,

4. and 6., pi. 40. f. 13—15.) Some of theseare of a larger size ( fig. 1651.); not more thanthree or four being found upon a single leaf(Easel Ins. Belust. Suppl., tab. 69.); whilstothers, which are as large as a boy’s marble,and perfectly globular, are often found singlyupon the leaves ; the last being produced by C.quercus folii. ( Reaum. Mem., tom. iii. pi. 39.fig. 13—17., pi. 37. fig. 10, 11., pi. 40. fig. 8.)

It is a curious circumstance connected withthese large globular galls (and which is alsoobserved in the gall nut), that, notwithstandingthe large size of the galls, only a single insect isenclosed therein; so that a very small portiononly of the centre of the gall is consumed, thecynips arriving at its perfect state within itssmall central prison, out of which it has to cutits way through a great portion of the solid sub-stance of the gall. The surface of the majority of these galls is smooth;some, however, are imbricated, and others are clothed with a woolly kind ofdown, similar in its nature to the outside of the bedeguar of the rose. A gallof this kind is figured in the Insect Architecture, p. 388., found upon the twig ofan oak; and in Dr. Nees von Esenbeck’s collection of minute Hymenoptera,at present in Mr. Westwood’s possession, there is a similar gall, of small size,upon an oak leaf, with the cynips by which it is produced ( C. quercus lanataNecs MSS.).

Oak Spangles. Amongst the excrescences found upon the leaves of the oak,are to be noticed the reddish insular scales on the under side of the oak leavesmentioned by Mr. Lowndes ( Gard. Mag., vol. xi. p. 691.), and supposed byhim to be parasitic plants. When full grown, they are about one eighth of an