British oak galls / by Edward T. Connold.

  • Edward Thomas Connold
Date:
1908
Catalogue details

Licence: In copyright

Credit: British oak galls / by Edward T. Connold. Source: Wellcome Collection.

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    deformities thus produced are well illustrated in Andricus aestivalis, which normally is cup-shaped ; B. aptera when solitary is globular. Three species of Neuroterus are often much out of shape on account of overcrowding, as may be seen on Plate LX, div. A ; and A. Sieboldi, B. renum and G. Kollari are at times subject to much distortion from the same cause. (b) Environment.—This also requires little more than a passing notice. Those galls whose normal position is on the under-surface of the leaf do not usually attain their customary dimensions when on the upper surface. A terminal, or nearly terminally situated, specimen of Aphilothrix callidoma is rarely as long as when axillary. G. Kollari is sometimes badly pinched in a forked twig (Plate XXXVI, figs. 9-14), or when bunched together in clusters (Plate XXXVIII). (b) Due to internal influences.—(a) Parasites are the principal agents in causing these modifications. They destroy the rightful owner of the gall, and in all unilocular galls growth is usually arrested; the struc- ture either remains a diminutive form of what it would have been, or some peculiarity is accentuated, such as the style on A. solitarius and on G. Kollari (see Plate XXXIX, div. C), or increase in the number of ridges on Aphilothrix callid.oma. (b) Inquilines do not usually destroy the larva, but only live within, and feed upon, the tissues of the gall in company with the owner, but not in the same larval cavity. In the majority of galls tenanted by inquilines no deviation from the normal dimensions are notice- able. This is exceedingly well exemplified in speci- mens of G. Kollari on Plate XXXIX, div. B. It is in every way normal, yet from it there have emerged the rightful owner and thirty-two inquilines, but their combined depredations have been so great as to leave the exterior a mere shell. Of all galls, whether on the oak or any other British plant, none appears to harbour more parasites and inquilines and visitors than that of Teras terminalis, 2
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