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The oak marble is frequently called the oak apple due to the superficial resemblance and the preponderance of the oak marble gall in the wild. Other galls found on oak trees include the oak artichoke gall and the acorn cup gall , but each of these has its own distinctive form.
The galls, shiny and hard, turn red in colour and then black or dark purple. [1] The asexual or parthenogenetic phase, about 10 mm across, [1] develops on acorn cups of English oak Q. robur and sessile oak Q. petraea. The galls, formed of flattened projections, often enclose the immature acorn. [1]
Galls (upper left and right) formed on acorns on the branch of a pedunculate (or English) oak tree by the parthenogenetic generation Andricus quercuscalicis.. The large 2 cm gall growth appears as a mass of green to yellowish-green, ridged, and at first sticky plant tissue on the bud of the oak, that breaks out as the gall between the cup and the acorn.
Galls may also provide the insect with physical protection from predators. [35] [24] Insect galls are usually induced by chemicals injected by the larvae of the insects into the plants and possibly mechanical damage. After the galls are formed, the larvae develop inside until fully grown, when they leave.
Andricus foecundatrix (formerly Andricus fecundator) is a parthenogenetic gall wasp which lays a single egg within a leaf bud, using its ovipositor, to produce a gall known as an oak artichoke gall, oak hop gall, larch-cone gall or hop strobile [1] [2] The gall develops as a chemically induced distortion of leaf axillary or terminal buds on pedunculate oak (Quercus robur) or sessile oak ...
Jumping oak galls are caused by a very tiny, native, stingless wasp (Neuroterus sp.) which lays eggs in leaf buds. As the leaf develops, pinhead-sized galls, also referred to as abnormal plant ...
The galls arise on young branches of the tree when gall wasps [4] sting the oak tree and deposit their larvae. The chemical reaction causes an abnormality in the tree, causing hard balls to be formed. They are corrugated in appearance.
Andricus quercusstrobilanus, the lobed oak gall wasp, is a species [1] of gall wasp in the family Cynipidae, [2] found in North America. [3] The quercus in its specific name is the genus name for oak, while "strobilus" is derived from the Greek strobilo which means "cone", a reference to the cone shape of the gall; [4] thus the gall is sometimes called pine cone oak gall.