Gall-forming
Guides
Adelges abietis
Pineapple-gall Adelgid, Eastern Spruce Gall Adelgid, Spruce Gall Aphid
Adelges abietis, commonly known as the pineapple-gall adelgid or eastern spruce gall adelgid, is a conifer-feeding insect that induces distinctive pineapple-shaped pseudocone galls on spruce shoots. The species is one of the most common adelgids in its genus and has been documented across Europe and North America. Unlike the closely related hemlock woolly adelgid (Adelges tsugae), A. abietis is not considered a major destructive pest, though its gall formation causes shoot deformation. The species exhibits strongly aggregated spatial distributions within and among host trees.
Asphondylia ceanothi
Ceanothus Bud Gall Midge
Asphondylia ceanothi is a gall midge in the family Cecidomyiidae that induces bud galls on Ceanothus plants. The species was described by Felt in 1908. Like other Asphondylia species, it manipulates plant tissue to form a protective gall structure where the larva develops. The specific host plant association is with Ceanothus species, a genus of flowering shrubs in the buckthorn family.
Asterolecaniidae
pit scales, asterolecaniids
Asterolecaniidae is a family of scale insects commonly known as pit scales. They are characterized by inducing depressions or pits in host plant tissues, often causing shoot distortion. The family contains approximately 25 genera and 243 described species, with greatest diversity in the northern hemisphere. Many species are associated with oaks, bamboos, and ornamental plants, and some form galls.
Calophya
jumping plant lice
Calophya is the type genus of the psyllid family Calophyidae, containing at least 69 described species. Members are gall-forming psyllids that feed on phloem and induce galls on host plants, primarily in the family Anacardiaceae. Several species have been investigated as biological control agents for invasive plants, particularly Brazilian peppertree (Schinus terebinthifolia). The genus shows high host specificity, with most species completing development only on specific host plants.
Cecidocharini
Cecidocharini is a tribe of tephritid fruit flies within the subfamily Tephritinae. The tribe contains eight recognized genera, including economically significant gall-forming species such as those in *Procecidochares*. Members are distinguished by their association with plant galls, a trait that separates them from many other tephritid groups. The tribe was established by Hering in 1947.
Colopha
Colopha is a genus of gall-forming aphids in the family Aphididae, first described by Monell in 1877. Species in this genus induce distinctive galls on host plants, most notably the elm cockscomb gall on American elm. The genus exhibits complex life cycles involving host alternation between woody plants and grasses, with both bisexual and unisexual reproductive strategies documented across species.
Colopha graminis
Colopha graminis is a gall-forming aphid in the family Aphididae, closely related to the well-studied elm cockscomb gall aphid Colopha ulmicola. Like other members of the genus Colopha, this species exhibits a complex life cycle involving host alternation and gall formation on its primary host, followed by migration to grass roots for summer feeding. The species was described by Monell in 1882 and belongs to the subfamily Eriosomatinae, a group characterized by their tendency to induce plant galls and their often elaborate seasonal host-switching behaviors.
Colopha ulmicola
Elm Cockscomb Gall Aphid
Colopha ulmicola is an aphid species that induces distinctive cockscomb-shaped galls on American elm leaves. It has a complex life cycle involving alternation between elm hosts and grass roots, with parthenogenetic reproduction within galls and sexual reproduction producing winged migrants that return to elm in autumn. The species is notable for its dramatic seasonal aerial migrations and its ability to manipulate plant development through chemical secretions.
Cynipidae
Gall Wasps, Gallflies
Cynipidae is a family of minute wasps (1–8 mm) renowned for inducing plant galls—abnormal growths that provide shelter and nutrition for developing larvae. The family comprises approximately 1,300 described species worldwide, with major radiations on oaks (Quercus) and roses (Rosa). Many species exhibit complex life cycles involving alternation of sexual and asexual (parthenogenetic) generations, often producing morphologically distinct galls. Gall induction involves chemical manipulation of host plant tissue, with enlarged venom glands implicated in this process. The family evolved from parasitoid ancestors and represents one of the most diverse groups of gall-forming insects.
Dentifibula viburni
Dentifibula viburni is a gall midge species (Diptera: Cecidomyiidae) originally described by Felt in 1907 as Contarinia viburni. The species is associated with Viburnum host plants, as indicated by its specific epithet. It belongs to the subfamily Cecidomyiinae, a group known for inducing plant galls. Very little published information exists regarding the biology, distribution, or economic significance of this particular species beyond its taxonomic description and nomenclatural history.
Eriosoma lanigerum
woolly apple aphid, woolly aphid, American blight
Eriosoma lanigerum is a small phloem-feeding aphid native to North America that has become a major worldwide pest of apple cultivation. Adults are concealed beneath dense white, cotton-like wax secretions produced from specialized abdominal glands, giving the species its common name. The aphid induces gall formation on both aerial and root tissues of host plants, disrupting vascular transport and potentially killing trees. Populations are primarily parthenogenetic in most regions, though sexual reproduction occurs where American elm (Ulmus americana) is present.
Eriosomatinae
Woolly Aphids, Gall-making Aphids
Eriosomatinae is a subfamily of aphids distinguished by filamentous waxy secretions that produce a cotton-like or woolly appearance. Members exhibit typically heteroecious holocyclic life cycles, alternating between primary and secondary host plants, with strong primary host plant specialization. Many species induce galls on primary hosts, particularly on Ulmaceae (elms, zelkovas), Salicaceae (poplars), and Anacardiaceae (sumacs). The subfamily contains three tribes: Eriosomatini, Fordini, and Pemphigini.
Eriosomatini
Eriosomatini is a tribe of gall-forming aphids in the subfamily Eriosomatinae, comprising approximately 140 species across 16 genera. All members induce galls on host plants in the family Ulmaceae, primarily on Ulmus (elms) and Zelkova species. The tribe exhibits complex life cycles with alternation between primary and secondary hosts, though some species have reduced or lost host alternation. Molecular studies have demonstrated that DNA sequencing can reliably associate morphologically distinct life stages to species, addressing a major identification challenge in the group.
Eurosta comma
Eurosta comma is a tephritid fruit fly that forms rhizome galls on goldenrod host plants (Solidago missouriensis). As a rhizome-galling specialist, it diverts host plant resources toward root tissue and away from vegetative growth, significantly reducing the host's ability to produce new rhizomes. The species interacts indirectly with other herbivores such as the leaf beetle Trirhabda canadensis by impairing the host plant's capacity to recover from defoliation.
Fordini
Fordini is a monophyletic tribe of gall-forming aphids (Hemiptera: Aphididae) characterized by complex two-year life cycles, strict host specificity, and sophisticated plant manipulation abilities. The tribe comprises two subtribes: Fordina, associated with Pistacia species and producing spherical to cauliflower-like galls; and Melaphidina, associated with Rhus species with galls positioned on leaf midribs and petioles. These aphids alternate between primary woody hosts where they induce conspicuous galls and secondary grass hosts where they feed on roots.
Gnorimoschema
Gnorimoschema is a genus of small moths in the family Gelechiidae, first described by Busck in 1900. The genus belongs to the tribe Gnorimoschemini and contains numerous species distributed across the Holarctic region, with particularly diverse faunas in North America and the Palaearctic. Several species are notable for their specialized life histories, including gall induction on host plants. The genus has been subject to extensive taxonomic revision, with many new species described in recent decades by researchers including Povolný and Powell.
Hormaphidinae
Hormaphidinae is a subfamily of aphids (Aphididae) distinguished by complex life cycles involving gall formation on primary host plants and often host alternation. The subfamily includes three tribes—Cerataphidini, Hormaphidini, and Nipponaphidini—with approximately 50 genera distributed primarily in eastern and southeastern Asia, with some representatives in North America. Many species produce specialized sterile soldiers for colony defense and exhibit diverse gall morphologies, from simple leaf curls to elaborate multi-cavity structures.
Hormaphis
witch hazel aphids, palm aphids
Hormaphis is a genus of gall-forming aphids in the family Aphididae, containing at least three described species distributed mainly in eastern North America. The genus includes the witch hazel cone gall aphid (H. hamamelidis), which induces distinctive cone-shaped galls on witch hazel (Hamamelis virginiana). Species in this genus exhibit complex host plant manipulation, including alteration of host phenolic metabolism to create favorable gall environments. The life cycle involves a bet-hedging strategy where eggs hatch before host budbreak to ensure gall formation opportunities.
Hormaphis hamamelidis
Witch-hazel Cone Gall Aphid
Hormaphis hamamelidis is a gall-forming aphid that induces distinctive red, cone-shaped galls on witch-hazel (Hamamelis virginiana) leaves. The species exhibits host alternation, with sexual reproduction and gall formation on witch-hazel in spring, followed by migration to birch (Betula) for parthenogenetic summer generations, and return migration to witch-hazel in autumn. Founding females (fundatrices) actively manipulate host plant phenolic metabolism, increasing condensed tannins and decreasing hydrolyzable tannins within galls to enhance their own reproductive success. Gall size, determined largely by fundatrix manipulation of plant growth, is the primary predictor of fundatrix fecundity rather than leaf position or plant vigor per se.
Liothrips ilex
toyon gall thrips
A gall-forming thrips species in the family Phlaeothripidae, Liothrips ilex is commonly known as the toyon gall thrips due to its association with toyon (Heteromeles arbutifolia). The species induces distinctive galls on host plant foliage. Like other phlaeothripids, it exhibits the typical thrips life history with propupal and pupal stages. The species has been documented in North America with over 1,000 iNaturalist observations, indicating it is relatively well-recorded where its host plant occurs.
Melaphis rhois
Staghorn sumac aphid, Sumac gall aphid
Melaphis rhois is a woolly aphid that induces distinctive galls on sumac leaves (Rhus typhina and R. glabra). It was first described by Asa Fitch in 1866 and has a complex life cycle involving alternation between sumac and moss hosts. The species is part of a cryptic species complex; molecular and morphometric analyses have revealed at least three sympatric species in North America previously grouped under this name. It exhibits exceptionally low genetic diversity and pronounced population structure due to restricted gene flow among isolated galls.
Meskea
Meskea is a genus of moths in the family Thyrididae, subfamily Siculodinae. Species in this genus are gall-forming herbivores whose larvae develop within stem galls on host plants in the family Malvaceae. The genus includes at least two documented species: Meskea horor, a potential biological control agent studied for its impact on weedy Sida species, and Meskea dyspteraria, which has been recorded as a host for the parasitoid wasp Calliephialtes grapholithae. Adult moths are crepuscular or nocturnal in habit.
Meunieriella
Meunieriella is a genus of gall midges (Diptera: Cecidomyiidae) established by Kieffer in 1909. Members of this genus are small, delicate flies in the subfamily Cecidomyiinae. The genus contains species that induce galls on host plants, though specific host associations and biological details remain poorly documented for many species. The genus is distinguished from related gall midge genera by particular combinations of adult morphological characters, though precise diagnostic features require specialist examination.
Mordwilkoja
Mordwilkoja is a genus of gall-forming aphids in the family Aphididae, subfamily Pemphiginae. Species in this genus induce galls on host plants and exhibit defensive behaviors against predators. The genus has been used as an outgroup in molecular studies of social behavior evolution in related aphid genera.
Ovaticoccus
Ovaticoccus is a genus of eriococcid scale insects in the family Eriococcidae. At least one species, Ovaticoccus amplicoxae from Belize, has been described with notably enlarged hind coxae. Some species in this genus induce leaf-curl galls on host plants.
Pemphigini
Pemphigini is a tribe of gall-forming aphids within the subfamily Pemphiginae. The tribe comprises two subtribes: Prociphilina, which typically induces pseudo-galls on leaves, and Pemphigina, which forms both pseudo-galls and true galls at various locations on host plants including leaf-petiole joints, petiole midpoints, and branches. Molecular phylogenetic studies indicate that Pemphigina is monophyletic, though the monophyly of Pemphigini as a whole is not supported. Gall morphology in this group appears to have evolved from open pseudo-galls to closed galls, with progressive relocation to more protected positions on the host plant.
Pemphigus populiglobuli
poplar bullet gall aphid
Pemphigus populiglobuli is a Nearctic aphid species known for forming bullet-shaped galls on poplar leaves during its primary generation. The Svalbard High Arctic population represents a remarkable secondary generation that has lost its primary host association and adapted to year-round root-feeding on grasses. Molecular analyses confirmed these specimens belong to P. populiglobuli rather than the historically assumed P. groenlandicus. The study proposes synonymizing P. groenlandicus and its subspecies crassicornis under P. populiglobuli based on morphometric similarity across Arctic and European populations.
Pemphigus populiramulorum
Poplar Twig Gall Aphid
Pemphigus populiramulorum is a gall-forming aphid in the family Aphididae, known from poplar (Populus) hosts. It induces distinctive twig galls on its primary host. The species has a complex life cycle involving host alternation, though specific secondary host details are not well documented in available sources. It has been confused with other root-feeding Pemphigus species in informal literature.
Pemphigus populitransversus
poplar petiole gall aphid, cabbage root aphid
Pemphigus populitransversus is a gall-forming aphid that induces distinctive fleshy galls on the petioles of poplar leaves. The species exhibits a complex life cycle involving alternation between primary hosts (Populus species) and secondary hosts in the Brassicaceae family. On poplars, females induce green or red galls up to 14 mm in diameter at leaf bases, where they lay eggs; a slit in the gall allows aphid exit. On Brassica hosts, the aphid forms root galls. Adults are small (1.6–2.6 mm) and morphologically distinct from other aphids in lacking abdominal cornicles and having relatively short antennae and legs.
Pemphigus spyrothecae
Poplar Spiral Gall Aphid
Pemphigus spyrothecae is a gall-forming aphid that induces distinctive spiral-shaped galls on leaf petioles of Populus nigra. The species exhibits eusocial behavior with a sterile soldier caste comprising first-instar nymphs with thickened hind legs that defend the colony against predators. Colony defense includes fortress defense, gall repair, and maintenance of colony hygiene. The aphid has a holocyclic life cycle with four generations: fundatrix, apterous virginoparae, alate sexuparae, and sexual males and females. Genetic relatedness within galls is high due to clonal reproduction, with clonal mixing averaging 0.68-10.4% across populations.
Philonix fulvicollis
Philonix fulvicollis is a gall wasp species in the family Cynipidae, first described by Fitch in 1859. It has an alternation of sexual and asexual generations, a phenomenon confirmed through molecular analysis of cytb and ITS2 sequences. The species is distributed across eastern and central North America, with records from the United States and Canada. Like other cynipid wasps, it induces gall formation on host plants, though specific host associations require further documentation.
Phylloxera caryaecaulis
Hickory Gall Phylloxera
Phylloxera caryaecaulis is a small, soft-bodied, gall-forming insect closely related to aphids. It induces distinctive globular galls on hickory leaves and petioles, primarily affecting mockernut hickory (Carya tomentosa) and other hickory species. The species overwinters as eggs deposited on bark or near old galls, with nymphs emerging during bud break in spring to initiate gall formation. Unlike some related phylloxeran species that attack pecan shoots and nuts, P. caryaecaulis is primarily a leaf-gall former and is not considered economically damaging to its host trees.
Phylloxera floridana
Phylloxera floridana is a species of phylloxeran, a small sap-sucking insect in the family Phylloxeridae. Phylloxerans are closely related to aphids and are known for inducing galls on host plants. The genus Phylloxera includes species that are significant agricultural pests, most notably the grape phylloxera (Daktulosphaira vitifoliae), though specific information about P. floridana's biology, host associations, and economic impact appears to be limited in available literature.
Phylloxera georgiana
Phylloxera georgiana is a gall-forming insect in the family Phylloxeridae, closely related to aphids. Like other phylloxerans, this species induces abnormal plant growths (galls) on its host plant through chemical secretions that manipulate plant development. The species was described by Pergande in 1904. Very few specific details about its biology, host associations, or distribution have been documented in the available literature.
Phylloxera paludis
Phylloxera paludis is a species of phylloxeran insect in the family Phylloxeridae, order Hemiptera. Phylloxerans are small, soft-bodied, sap-sucking insects closely related to aphids. Members of the genus Phylloxera are known for inducing gall formation on host plants through chemical secretions that alter plant tissue development. The specific epithet "paludis" suggests an association with marsh or wetland habitats, though detailed ecological studies of this particular species appear limited in the available literature.
Phylloxera perniciosa
pecan phylloxera
Phylloxera perniciosa, commonly known as the pecan phylloxera, is a gall-forming insect that attacks shoots and nuts of pecan trees (Carya illinoinensis). It is considered the most damaging phylloxera species affecting pecans, causing galls that reduce yield, impair tree vitality, and curtail subsequent production. The insect is closely related to aphids and survives winter as eggs in bark crevices. Unlike the pecan leaf phylloxera, which only forms galls on leaves, this species attacks reproductive and vegetative shoots, making it economically significant in commercial pecan production.
Phylloxera picta
Phylloxera picta is a species of gall-forming insect in the family Phylloxeridae, closely related to aphids. Like other phylloxerans, it induces abnormal plant growths (galls) on host trees through chemical secretions that manipulate plant tissue development. The species overwinters as eggs and has a complex life cycle involving multiple generations and both winged and wingless forms.
Phylloxera rimosalis
pecan leaf phylloxera
Phylloxera rimosalis is a tiny, soft-bodied insect closely related to aphids that forms galls exclusively on pecan leaves. It is one of two economically important phylloxera species attacking pecans, the other being the more damaging pecan phylloxera (Phylloxera devastatrix) which attacks shoots and nuts. Extensive infestations of P. rimosalis may cause some defoliation, but the species is generally less destructive than its congener. The insect has been observed in Texas and is managed as a pest of commercial pecan orchards.
Phylloxera russellae
Phylloxera russellae is a small, soft-bodied insect in the family Phylloxeridae, closely related to aphids. Like other phylloxerans, it induces gall formation on host plants through chemical secretions that manipulate plant tissue development. The species was described by Stoetzel in 1981. Members of the genus Phylloxera are known for complex life cycles involving multiple generations and forms, including winged and wingless morphs.
Phylloxera stanfordiana
Phylloxera stanfordiana is a species of phylloxeran insect in the family Phylloxeridae, order Hemiptera. It is closely related to aphids and shares their soft-bodied morphology and plant-feeding habits. The species was described by Ferris in 1919. Like other phylloxerans, it is known to induce gall formation on host plants through its feeding activity. The specific epithet 'stanfordiana' refers to Stanford University, where the type specimen was collected in 1904.
Phylloxera stoetzelae
Phylloxera stoetzelae is a species of phylloxeran, a group of tiny, soft-bodied, sap-sucking insects closely related to aphids. Members of the genus Phylloxera are known for inducing galls on host plants through chemical secretions that stimulate abnormal plant tissue growth. The species was named in honor of entomologist Mark Stoetzel. Like other phylloxerans, it likely completes a complex life cycle involving both parthenogenetic and sexual reproduction phases, with overwintering eggs hatching in spring to initiate gall formation on new growth.
Phylloxera symmetrica
Phylloxera symmetrica is a gall-forming insect in the family Phylloxeridae, closely related to aphids. Like other phylloxerans, this species induces abnormal plant growths (galls) on host plants through chemical secretions that manipulate plant development. The species was described by Pergande in 1904. Members of the genus Phylloxera are known for complex life cycles involving both sexual and asexual generations, with overwintering eggs and multiple gall-forming generations per year.
Phylloxera tuberculifera
Phylloxera tuberculifera is a gall-forming insect species in the family Phylloxeridae, first described by Duncan in 1922. As with other phylloxerans, this species induces abnormal plant growths (galls) on host plants through chemical secretions that redirect plant tissue development. The species belongs to a genus containing several economically significant pests, particularly of pecan and grape. Specific host associations and detailed biology for P. tuberculifera remain poorly documented in published literature.
Smynthurodes
Smynthurodes is a genus of gall-forming aphids in the family Aphididae. The genus includes at least one well-documented species, Smynthurodes betae, which induces galls on host plants. Gall formation in this genus appears to be constrained by host plant phenology rather than active site selection by colonizing aphids. The genus has been recorded from parts of northern Europe.
Tamalia
Ericaceous Gall Aphids, Manzanita Leaf Gall Aphids
Tamalia is a Nearctic genus of gall-forming aphids and the sole genus in the subfamily Tamaliinae. Eight described species induce galls on woody plants in the heath family (Ericaceae), primarily on manzanita (Arctostaphylos) and related genera. The genus exhibits a distinctive social system in which multiple foundresses co-occupy galls, a trait that has been exploited by the evolution of socially parasitic inquiline species within the same genus.
Tamaliinae
Tamaliinae is a small subfamily of aphids (Aphididae) containing the Nearctic genus Tamalia. Members are obligate gall-formers on woody plants in the family Ericaceae, including Arctostaphylos, Arbutus, and Comarostaphylis. The subfamily exhibits social behavior, with foundresses co-occupying galls and high relatedness among colony members. Some species act as inquilines, acting as obligate parasites within galls of other Tamalia species.
Tetraneura
elm-grass root aphids, woolly elm aphids
Tetraneura is a genus of gall-forming aphids in the family Aphididae, comprising more than 30 described species. These aphids are heteroecious, alternating between primary hosts in the genus Ulmus (elms), where they induce characteristic galls on leaves, and secondary hosts in the family Poaceae (grasses), where they feed on roots. The genus is notable for complex host manipulation, with species capable of altering host plant biochemistry to create nutritional sinks within galls. Several species, including the alien T. nigriabdominalis, are expanding their ranges in Europe and pose potential threats to cereal crops such as maize.
Tetraneura ulmi
elm sack gall aphid, fig gall aphid
Tetraneura ulmi, commonly known as the elm sack gall aphid or fig gall aphid, is a gall-forming aphid in the family Aphididae. First described by Linnaeus in 1758, this species induces distinctive club-like pouch galls on elm leaves. The aphid exhibits a complex life cycle involving alternation between primary elm hosts and secondary grass hosts. Founding mothers stimulate gall formation through sap-sucking behavior, creating a protected environment for their offspring. The species is distributed across Asia, Europe, and North America, with particular dominance in northwestern Europe.
Trigonorhinus
fungus weevils
Trigonorhinus is a genus of fungus weevils in the beetle family Anthribidae, comprising approximately 15-16 described species. The genus includes wood-boring species that develop in plant tissues, with at least one species documented as a pest of Caragana liouana in arid regions of China. A notable species, Trigonorhinus sp., has been demonstrated to rely on gut bacterial symbionts for production of male aggregation pheromones essential for mate attraction.