An oak is a hardwood tree or shrub in the genus Quercus of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne in a cup. The genus is widely distributed in the Northern Hemisphere; it includes some 500 species, both deciduous and evergreen. Fossil oaks date back to the Middle Eocene. Molecular phylogeny shows that the genus is divided into Old World and New World clades, but many oak species hybridise freely, making the genus's history difficult to resolve.
Quercus robur, the pedunculate oak, is a species of flowering plant in the beech and oak family, Fagaceae. It is a large tree, native to most of Europe and western Asia, and is widely cultivated in other temperate regions. It grows on soils of near neutral acidity in the lowlands and is notable for its value to natural ecosystems, supporting a very wide diversity of herbivorous insects and other pests, predators and pathogens.
Galls or cecidia are a kind of swelling growth on the external tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissues, similar to benign tumors or warts in animals. They can be caused by various parasites, from viruses, fungi and bacteria, to other plants, insects and mites. Plant galls are often highly organized structures so that the cause of the gall can often be determined without the actual agent being identified. This applies particularly to some insect and mite plant galls. The study of plant galls is known as cecidology.
Quercus cerris, the Turkey oak or Austrian oak, is an oak native to south-eastern Europe and Asia Minor. It is the type species of Quercus sect. Cerris, a section of the genus characterised by shoot buds surrounded by soft bristles, bristle-tipped leaf lobes, and acorns that usually mature in 18 months.
Gall wasps, also traditionally calledgallflies, are hymenopterans of the family Cynipidae in the wasp superfamily Cynipoidea. Their common name comes from the galls they induce on plants for larval development. About 1,300 species of this generally very small creature are known worldwide, with about 360 species of 36 different genera in Europe and some 800 species in North America.
Oak apple or oak gall is the common name for a large, round, vaguely apple-like gall commonly found on many species of oak. Oak apples range in size from 2 to 4 centimetres in diameter and are caused by chemicals injected by the larva of certain kinds of gall wasp in the family Cynipidae.
Andricus kollari, also known as the marble gall wasp, is a parthenogenetic species of wasp which causes the formation of marble galls on oak trees. Synonyms for the species include Cynips kollari, Andricus quercusgemmae, A. minor, A. indigenus and A. circulans.
Andricus foecundatrix 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 The gall develops as a chemically induced distortion of leaf axillary or terminal buds on pedunculate oak or sessile oak trees. The larva lives inside a smaller hard casing inside the artichoke and this is released in autumn. The asexual wasp emerges in spring and lays her eggs in the oak catkins. These develop into small oval galls which produce the sexual generation of wasps. A yew artichoke gall caused by the fly Taxomyia taxi also exists, but is unrelated to the oak-borne species. Previous names or synonyms for the species A. fecundator are A. fecundatrix, A. pilosus, A. foecundatrix, A. gemmarum, A. gemmae, A. gemmaequercus, A. gemmaecinaraeformis and A. quercusgemmae.
Cola-nut galls develop as a chemically induced distortion of leaf axillary or terminal buds on pedunculate oak or sessile oak trees, caused by the agamic gall wasp Andricus lignicola which lays single eggs within leaf buds using their ovipositor. A previous name or synonym for the species A. lignicola is A. lignicolus and A. venheurni.
The common spangle gall on the underside of leaves and the currant gall on the male catkins or occasionally the leaves, develop as chemically induced distortions on pedunculate oak, or sessile oak trees, caused by the cynipid wasp Neuroterus quercusbaccarum which has both agamic and bisexual generations.
Andricus grossulariae is a gall wasp species inducing agamic acorn cup galls on oak tree acorn cups and sexual phase galls on catkins. Synonyms include Andricus fructuum, Andricus gemellus, Andricus intermedius, Andricus mayri and Cynips panteli.
Andricus dentimitratus is a gall forming wasp in the genus Andricus. The adults lay their eggs on various species of oak and the developing larvae causes the trees to create a large ornate gall. The oaks parasitised include Quercus frainetto, Q. petraea, Q. pyrenaica, Q. pubescens and Q. robur. The gall is formed out of the cup of the acorn. In cross-section it resembles a mushroom. It is woody, maroon, shiny and sticky. It grows up to 25 mm high and 20 mm wide. What resembles the head of the mushroom is lobed or toothed in various ways. The insect emerges from the narrowing, between the head and base.
Andricus quercuscalifornicus, or the California gall wasp, is a small wasp species that induces oak apple galls on white oaks, primarily the valley oak but also other species such as Quercus berberidifolia. The California gall wasp is considered an ecosystem engineer, capable of manipulating the growth of galls for their own development. It is found from Washington, Oregon, and California to northern regions of Mexico. Often multiple wasps in different life stages occupy the same gall. The induced galls help establish complex insect communities, promoting the diversification in niche differentiation. Furthermore, the adaptive value of these galls could be attributed their ecological benefits such as nutrition, provision of microenvironment, and enemy avoidance.
Andricus aries is a species of gall-forming wasps, in the genus Andricus. The species was named by the French entomologist Joseph-Étienne Giraud, in 1859. It is commonly found in eastern Europe and during the 21st century has spread to western Europe.
Andricus curvator is a gall wasp which forms chemically induced leaf galls on oak trees and has both agamic and sexual generations. Agamic and sexual generations usually form two distinct galls on oak trees, but in the case of A. curvator there are six galls; the sexual generation usually on the leaf, occasionally in a twig or catkin, and the agamic generation in a bud. The wasp was first described by Theodor Hartig, a German biologist, in 1840 and is found in most of Europe.
Andricus corruptrix is a species of gall-forming wasp, in the genus Andricus. It is found in Europe.
Andricus inflator is a species of gall-forming wasps, in the genus Andricus, which has a sexual and an asexual generation, producing two different galls. The wasp was named by the German biologist Theodor Hartig, in 1840 and is found in Europe.
Andricus infectorius is a species of gall-forming wasp. The species was named by the German biologist Theodor Hartig, in 1843 and is found in Europe.
Andricus mukaigawae is a species of gall wasp native to southeastern Asia. It creates galls on the buds and leaves of oak trees. The galls are sometimes used by other gall wasps unable to create galls of their own, with both species sharing the gall.
Andricus hispanicus is a parthenogenetic species of wasp which causes the formation of marble galls on oak trees. The galls caused by the agamous generation are similar to the closely related Andricus kollari.
