Andricus kollari, also known as the marble gall wasp, is a species of wasp which causes the formation of marble on oak trees. Synonyms for the species include Cynips kollari, Andricus quercusgemmae, A. minor, A. indigenus and A. circulans.
In May or June, a sexual female lays her eggs in the developing buds of susceptible oak trees using her ovipositor. Chemicals produced by both the adult and developing wasps cause the formation of a gall. Pedunculate oak ( Quercus robur), sessile oak ( Quercus petraea) and the hybrid Quercus × rosacea can all be parasitized.Redfern M., Shirley P., Bloxham M., British Plant Galls Second Edition, Field Studies Council, Shrewsbury, 2011 The host trees are often immature or retarded specimens; galls are rarer on older, healthier trees.Darlington, Arnold (1968). The Pocket Encyclopaedia of Plant Galls in colour. Pub. Blandford Press. Dorset. P. 154. The Turkey oak ( Quercus cerris), introduced into Great Britain in 1735, is required for the completion of the wasp's life cycle. The oak marble gall is frequently conflated with the oak apple gall, caused by another gall wasp, Biorhiza pallida. Oak marble galls are also known as the bullet gall, oak nut or Devonshire gall. Lincolnshire Wildlife Trust website
The developing spherical galls are green at first, brown later, and mature in August. Each gall contains a central chamber, with a single female wasp larva of the asexual generation, which emerges through a 'woodworm-like' hole as an adult winged gall-wasp in September. These asexual (agamic) females lay unfertilized eggs in the embryonic bud leaves of the Turkey oak, with galls slowly developing during winter, and are visible in March and April as small oval structures between the bud scales, looking like ant's eggs or pupae. The British Oak. Its History and Natural history. Ed. Morris, M.G. & Perring, F.H (1974) . Pub. Bot. Soc. Brit. Isles. P. 309. The emerging adult gall-wasps in spring are the sexual generation, producing both males and females, which fly to the common oaks to initiate the formation of the summer marble gall.
The abnormal buds develop during the summer and the bud is wholly replaced by the growing gall. Marble galls may remain attached to the tree for several years. Oak Marble Gall details The level of attack by the insect varies greatly from year to year. Royal Horticultural Society website.
A. hispanicus was previously included in A. kollari, but the two are genetically distinct
Fused and/or stunted specimens can be confused with A. lignicola (Hartig), the "Cola-nut gall".Redfern, Margaret & Shirley, Peter (2002). British Plant Galls. Identification of galls on plants & fungi. AIDGAP. Shrewsbury : Field Studies Council. . Page 404.
A number of insect live harmlessly within the oak marble gall. Some of these, as well as Andricus itself, are parasite by insects referred to as parasitoids. The chalcid wasp Torymus nitens is an example of a parasitoid in oak marble galls. A parasitoid wasp The presence of these inquilines and parasites is often visible on older galls by the presence of fine exit-holes, smaller than that of the gall wasp itself.
A gall can contain the cynipid wasp as the host that made the gall; up to five species of inquilines ( Ceroptres clavicornis, Synergus gallaepomiformis, S. pallidipennis, S. reinhardi and S. umbraculus) eating the host's food; as well as up to thirteen parasitoid species ( Eurytoma brunniventris, Sycophila biguttata, S. variegata, Megastigmus dorsalis, M. stigmatizans, Torymus geranii, T. auratus, Caenacis lauta, Hobbya stenonota, Mesopolobus amaenus, M. fasciiventris, M. sericeus, Eupelmus urozonus) living on the host, inquilines and each other. A Checklist of British Species.
Many old galls bear numerous dark brown excrescences, due to the fungus Phoma gallorum.
British galls have too little tannic acid (about 17%) for the best results; Aleppo galls have three times as much.
Powdered galls mixed with hog's lard and applied to the posterior were said to be good for curing Hemorrhoid.Brook, Richard. New Cyclopaedia of Botany and Complete Book of Herbs. London : W. M. Clark. p. 497.
Oak marble gall extract is used in deodorants because of tannic acid's anti-bacterial properties. Deodorant. Accessed : 2010-08-15
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