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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    when above ground. I have observed that when situated on the trunk, or a branch, the majority of single growths (i.e. like that in Plate XXX, div. A), approach a reniform or an oval shape, and are s.essile. Such a specimen may be regarded as the result of the oviposition of but one imago, whereas that in the lower half of Plate XXYI, being due to several, perhaps four, imagines. The size, likewise, differs considerably, varying from that of a marble to upwards of 30 cm. at greatest girth. The gall appears in September and continues grow- ing for some weeks. About November it ceases to grow until the spring, when formation is resumed, and by the end of the summer it is mature ; the larvse then pupate and remain in that condition through the winter, the imagines coming out about April. During formation the gall is succulent, of the consistence of a potato, more or less smooth externally and slightly glossy; when nearing maturity it becomes firmer, and finally hard and woody. Small and medium size aerial specimens usually have about half their surface deeply furrowed, producing elevations of irregular shape, size, and height, and mostly pointed. The larval chambers are exceedingly numerous. They are normally globular in shape, about 3 mm. in diameter, with thin, hard, and woody walls, firmly affixed to each other in a somewhat concentric pattern, and occupying the centre of the surrounding tissue. After the gall has arrived at maturity this tissue undergoes various changes. It loses much of its solid nature, becomes soft and open in texture, thus offering little resistance to the imagines in eating their way to the exterior. Finally it decays away, leaving the tenantless larval chambers in a conglomerated con- dition, whitish in colour, and adherent for some time. The colour is regulated according to situation. Below ground it is white, or dirty white, sometimes with a rose tinge ; beneath leaves or moss it is suffused
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