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.
Neuroterus is a genus of gall wasps that induce galls on oaks in which the wasp larvae live and feed. Some species produce galls that fall off the host plant and 'jump' along the ground due to the movement of the larvae within.
Andricus is a genus of oak gall wasps in the family Cynipidae.
Cynipini is a tribe of gall wasps. These insects induce galls in plants of the beech and oak family, Fagaceae. They are known commonly as the oak gall wasps. It is the largest cynipid tribe, with about 936 to 1000 recognized species, most of which are associated with oaks. The tribe is mainly native to the Holarctic.
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 opertus, the fimbriate gall wasp, is a species of wasp in the family Cynipidae whose bisexual generation induces elongate, spiky galls on the leaves of various species of oaks in California, including valley oak and scrub oak. The galls of the bisexual generation form in spring, adults emerge in late spring, and galls persist on trees until the fall. The unisexual generation of this species forms aborted bud galls in the summer and fall.
Feron kingi, the red cone gall wasp, is a species of gall wasp in the family Cynipidae.
Druon fullawayi, also known as the yellow wig gall wasp, is a species of gall wasp in the family Cynipidae. It was previously placed in the genus Andricus. William Beutenmüller described the female adult wasps as 1.5-2.25 mm long, black with brown mouth parts and brown legs. The galls of D. fullawayi are tan or yellow, woolly, and measure 5-8 mm in diameter. Each gall holds a single chamber for larvae. They are found in California on oak trees, especially Quercus lobata.
Feron crystallinum, also known as the crystalline gall wasp, is a species of gall-forming wasp in the genus Feron. The galls of its all-female parthenogenic generation are pink and covered in hairs that are white, red, or brown. These galls are often massed together in clumps that can cover the underside of leaves. Individual galls are 12–14 mm high, 7 mm across, and have a single chamber for larvae. This generation emerges in late winter. In the spring, the bisexual generation of males and females induces much smaller galls with shorter hairs. F. crystallinum galls are found in all species of oaks in California.
Feron parmula, also known as the disc gall wasp, is a species of oak gall wasp in the genus Feron. It induces galls in a wide selection of oak species, especially white oaks, and including hybrids. The galls are disc-shaped, up to 3 mm in diameter, and pale with red streaking. Adult females emerge in April. The galls induced by F. parmula superficially resemble the galls of Feron gigas,Andricus viscidus, and newly identified species called the "plate gall wasp" and the "orange-cap gall wasp" by Ronald Russo. Galls induced by this wasp have been documented in Oregon and California on the Pacific coast of North America.
Feron gigas, also known as the saucer gall wasp, is a species of gall-forming wasp in the genus Feron. It induces galls on the leaves of scrub oaks, blue oaks, and Engelmann oaks. The galls produced by its all-female generation, which emerges in winter, are 3-4 mm wide, circular with raised edges. They are red, pink, brown, or purple. The larval chamber exists as a raised bump in the gall's center. The bisexual generation produces galls that are brown and cone-shaped.
Feron pattersonae, also known as the plate gall wasp, is a species of oak gall wasp in the genus Feron. Their hosts are among the white oaks grouping of oaks, with blue oak being common.
Trichoteras vacciniifoliae, formerly Andricus vacciniifoliae, the golden oak apple wasp, is a species of gall-forming hymenopteran. The wasp creates a stem gall on host plants, namely huckleberry oaks and canyon live oaks. Andricus vacciniifoliae is native to the west coast of North America. Because of their colorful appearance and location on the plant, the galls are often mistaken for fruit. The larval chamber is at the center of the gall, connected to the husk by slender, radiating fibers.
Feron atrimentum, also known as the striped volcano gall wasp, is a species of gall-forming wasp in the genus Feron. It induces galls on blue oak leaves. Like other oak gall wasps, it has two generations: a bisexual generation, and a parthenogenic female generation. The bisexual generation produces round, 3–4 millimetres (0.12–0.16 in) galls in spring that start as green or pink, and then turn brown. The unisexual generation produces conical, 4–4 millimetres (0.16–0.16 in) galls in summer that are pale with red stripes.
Andricus brunneus, also known as the clustered gall wasp, is a species of oak gall wasp in the genus Andricus. It lives along the Pacific Coast of North America. Only females of this species are known. Adults are brown or reddish-brown and about 3 millimetres (0.12 in) long. It induces round galls on the leaves of white oaks, especially blue oaks. These galls are usually found in clusters, reddish to light brown, and about 6 millimetres (0.24 in) in diameter. Each holds a single larval chamber, from which adult females emerge in autumn.
Feron bakkeri, also known as the pinched leaf gall wasp, is a relatively uncommon species of gall-inducing hymenopteran. They produce pink leaf galls on Oregon oaks and scrub oaks. The distribution of this wasp is California and Oregon in North America. It was previously placed in the genus Andricus.
Trichoteras coquilletti, formerly Andricus coquilletti, also known as the little oak-apple gall wasp, is a fairly common species of cynipid wasp that produces galls on oak trees in North America. This wasp oviposits on the underside of the leaves of huckleberry oaks and canyon live oaks. The larval chamber is at the center of the gall, connected to the husk by slender, radiating fibers.
Callirhytis congregata, formerly Andricus congregata, the sausage flower gall wasp, is a species of hymenopteran that induces galls on the catkins of coast live oaks, interior live oaks, and canyon live oaks in California in North America. This wasp is considered locally common. William Harris Ashmead described Andricus congregatus as producing a gall like a "rugose, yellowish brown woody swelling, containing numerous cells growing apparently from the extreme tips of very slender twigs of Quercus chrysolepis, the gall appearing to have a long peduncle".
Atrusca brevipennata, formerly Andricus pellucidus, also known as the little oak-apple gall wasp, is a locally common species of cynipid wasp that produces galls on oak trees in North America. The wasp oviposits on shrub live oak and Gambel oak leaves. The larval chamber is at the center of the gall, connected to the husk by slender, radiating fibers. This wasp is most commonly observed in the American Southwest, as far north as Denver. It is visually similar to, and may be confused with, Atrusca bella.
Besbicus maculosus, formerly Andricus maculosus and Cynips maculosa, also known as the pear gall wasp, is an uncommon species of cynipid wasp that induces galls on oak trees on the west coast of North America. The wasp oviposits on leather oak and scrub oak leaves. Fresh galls are green. This wasp has been observed in California.
