Gall-former
Guides
Phylloxera notabilis
Pecan Leaf Phylloxera
Phylloxera notabilis is a gall-forming insect in the family Phylloxeridae, closely related to aphids. It is a significant pest of pecan trees (Carya illinoinensis), forming characteristic galls on leaf tissue. The species has host-associated populations on both pecan and water hickory (Carya aquatica), with documented differences in bacterial diversity between these populations. Unlike the more destructive pecan phylloxera (Phylloxera devastatrix), which attacks shoots and nuts, P. notabilis primarily damages leaves and may cause defoliation in heavy infestations.
Phylloxera pilosula
Phylloxera pilosula is a gall-forming insect in the family Phylloxeridae, closely related to aphids. Like other phylloxerans, it induces abnormal plant growths (galls) on its host plants through chemical secretions that manipulate plant tissue development. The species was described by Pergande in 1904. Specific host associations and detailed biology for this particular species remain poorly documented in available literature.
Phylloxera querceti
Phylloxera querceti is a gall-forming insect in the family Phylloxeridae, closely related to aphids. The species induces abnormal plant growths (galls) on oak species (Quercus), within which it develops and feeds. Like other phylloxerans, it has a complex life cycle involving both sexual and parthenogenetic generations, with overwintering eggs hatching in spring to produce fundatrices that initiate gall formation. The specific host associations and gall morphology distinguish it from congeners such as the economically significant grape phylloxera (Daktulosphaira vitifoliae).
Phylloxera rileyi
Phylloxera rileyi is a gall-forming insect in the family Phylloxeridae, closely related to aphids. The species is known from limited observations and taxonomic records, with only two documented observations on iNaturalist. Like other phylloxerans, it likely induces abnormal plant growths (galls) on host plants through chemical secretions that manipulate plant development. The species was described by Riley in 1874.
Phylloxera spinosa
Phylloxera spinosa is a gall-forming insect in the family Phylloxeridae, closely related to aphids. This species induces distinctive galls on its host plants through chemical secretions that manipulate plant tissue development. Like other phylloxerans, it has a complex life cycle involving multiple generations and winged dispersal forms. The species was described by Shimer in 1869 and is currently accepted as valid.
Phylloxera subelliptica
Phylloxera subelliptica 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 tissue development. The species was described by Shimer in 1869. Phylloxerans typically have complex life cycles involving multiple generations and both sexual and parthenogenetic reproduction.
Phylloxera texana
Phylloxera texana is a species of gall-inducing insect in the family Phylloxeridae, described by Stoetzel in 1981. Like other phylloxerans, it is closely related to aphids and induces abnormal plant growths (galls) on its host plants through chemical secretions that manipulate plant tissue development. The species is presumably associated with pecan or related hickory species given its genus affiliation and geographic name, though specific host records and detailed biology remain poorly documented in available literature.
Phylloxera wiedenmanni
Phylloxera wiedenmanni is a gall-forming phylloxeran that induces galls on hickory trees. As a member of the family Phylloxeridae, it is closely related to aphids and shares their piercing-sucking mouthpart morphology. The species overwinters as eggs deposited on bark or near old galls, with nymphs emerging during bud break to feed on new leaf tissue. Its feeding stimulates the formation of globular galls on leaves and petioles, within which the insect completes development. The species exhibits complex life history traits including parthenogenetic reproduction within galls and winged dispersal forms.
Phylloxeridae
phylloxerans, phylloxerids
Phylloxeridae is a small family of plant-parasitic hemipterans comprising approximately 75 described species across 11 genera and two subfamilies (Phylloxerininae and Phylloxerinae). These minute insects are closely related to aphids and adelgids, with which they share the superfamily Phylloxeroidea. They are specialized gall-formers on deciduous trees and perennial fruit crops, with complex life cycles involving cyclical parthenogenesis and host alternation between primary woody hosts and secondary herbaceous hosts. The family includes the economically devastating grape phylloxera (Daktulosphaira vitifoliae), responsible for the 19th-century European vineyard crisis.
Phylloxerina
Phylloxerina is a genus of phylloxerids—small, sap-sucking true bugs in the family Phylloxeridae. These insects are closely related to aphids and are known for inducing distinctive leaf galls on host plants. The genus includes species such as Phylloxerina nyssae, which forms crescent-shaped galls on black tupelo (Nyssa sylvatica). Phylloxerids are morphologically unusual among Sternorrhyncha, with wax-covered bodies and complex life cycles involving both gall-dwelling and bark-dwelling generations. The genus is native to northern North America.
Phylloxerina nyssae
Phylloxerina nyssae is a minute gall-forming phylloxerid that induces distinctive yellowish-white crescent-shaped galls along the leaf margins of Nyssa sylvatica (black tupelo or sour gum). Adults are approximately 1 mm in length with sucking mouthparts positioned between the first pair of legs. The species reproduces asexually within galls, with females producing dozens of pill-shaped translucent eggs. Overwintering occurs as wax-covered individuals concealed in bark crevices and craggy trunk folds. While the gall formation causes cosmetic damage to foliage, the tree remains otherwise healthy.
Pineus pinifoliae
Pine Leaf Adelgid, Pine Leaf Aphid, Pine Leaf Chermid
Pineus pinifoliae is a small, phloem-feeding insect in the family Adelgidae, commonly known as the pine leaf adelgid or pine leaf aphid. It has a complex life cycle involving alternation between spruce (Picea) as the primary host, where it forms galls on new shoots, and white pine (Pinus strobus) as the secondary host. The species produces multiple generations annually, with distinct morphological forms including winged migrants that transfer between hosts. Heavy infestations on white pine cause characteristic damage patterns including needle stunting, reduced radial growth, and branch mortality concentrated in the lower and mid-crown.
Pineus similis
Ragged Spruce Gall Adelgid
Pineus similis is a gall-forming adelgid that induces galls on spruce trees (Picea spp.). Originally described as Chermes similis by Gillette in 1907 from blue spruce in Colorado, it was later transferred to genus Pineus by Annand. The species produces winged females that emerge from galls and settle on spruce hosts, with documented preference for white spruce. Wingless females bearing egg clusters occur within galls. It has been recorded on multiple spruce species across North America and has doubtful or rare records in Europe.
Pinyonia
Pinyon Spindle Gall Midge
Pinyonia is a genus of gall midges in the family Cecidomyiidae. The genus contains at least one described species, P. edulicola, which forms spindle-shaped galls on pinyon pine needles. These insects are small flies that induce abnormal plant growth through larval feeding activity.
Podapion
pine gall weevils
Podapion is a genus of weevils in the family Brentidae, commonly known as pine gall weevils. The genus contains species that induce gall formation on pine trees, with documented life cycles spanning multiple years. Research on Podapion gallicola indicates a three-year developmental period involving specific gall induction on host branches.
Podapion gallicola
Pine Gall Weevil
Podapion gallicola is a weevil that induces galls on pine branches. It has a three-year life cycle on its host tree, with adults emerging in June and ovipositing through August. Larvae feed gregariously on cambium and xylem tissue, triggering gall formation during their second instar. The species is known from Michigan and eastern Canada.
Procecidochares
gall flies
Procecidochares is a genus of tephritid fruit flies comprising approximately 20 described species. All members are gall-formers on Asteraceae plants, with larvae developing within stem or branch galls. The genus has gained significant attention for the species P. utilis, widely deployed as a biological control agent against the invasive weed Ageratina adenophora. Research on Procecidochares has contributed to understanding host selection genetics and sympatric speciation mechanisms in phytophagous insects.
Prociphilus
Woolly Aphids
Prociphilus is a genus of woolly aphids in the family Aphididae, subfamily Eriosomatinae, comprising approximately 50 species. These aphids are notable for inducing gall formation on host plants, within which they reside and feed. The genus exhibits complex life cycles including host alternation and polyphenism, with multiple distinct morphs adapted to different hosts and conditions. Several species have documented mutualistic relationships with ants, and some display remarkable seasonal phenomena such as the mass emergence of Prociphilus oriens in Japan, which is culturally associated with the first snowfall.
Prodiplosis violicola
Prodiplosis violicola is a species of gall midge in the family Cecidomyiidae, first described by Coquillett in 1900. As a member of the genus Prodiplosis, it belongs to a group of cecidomyiids known for inducing galls on host plants. The species epithet 'violicola' suggests an association with Viola species (violets), though specific host relationships require verification.
Protaplonyx sarcobati
Greasewood Leaf Gall
Protaplonyx sarcobati is a gall midge in the family Cecidomyiidae, known for inducing galls on leaves of greasewood (Sarcobatus vermiculatus). The species was originally described by Felt in 1914 as Aplonyx sarcobati and later transferred to Protaplonyx. It is documented from limited observations in western North America.
Psylloidea
jumping plant lice, psyllids, psylloids
Psylloidea is a superfamily of true bugs (Hemiptera) in the suborder Sternorrhyncha, commonly known as jumping plant lice or psyllids. The group comprises approximately 3,800 described species classified into seven extant families: Aphalaridae, Calophyidae, Carsidaridae, Liviidae, Mastigimatidae, Psyllidae, and Triozidae. Fossil evidence indicates the superfamily originated in the Early Jurassic, though modern families do not appear until the Eocene. Psyllids are obligate phloem-feeders, typically exhibiting high host specificity with most species restricted to a single plant species or closely related group. Many species are economically significant agricultural pests, notably as vectors of bacterial and viral plant pathogens.
Rhinocola aceris
Sycamore psyllid
Rhinocola aceris is a psyllid species in the family Aphalaridae, commonly known as the sycamore psyllid. It is associated with sycamore maple (Acer pseudoplatanus) and related maple species. The species was originally described by Linnaeus in 1758 as Chermes aceris. Like other psyllids, it feeds on plant sap and can cause gall formation on host leaves.
Rhopalomyia clarkei
Rhopalomyia clarkei is a gall midge species in the family Cecidomyiidae, first described by Felt in 1907. The species induces small, conical, single-chambered galls on two host plants: Solidago altissima and Solidago rugosa. It occurs in north-eastern and north-central North America. Adult females are approximately 2 mm long with a dull red abdomen and 17 antennal segments.
Rhopalomyia ericameriae
Rosette Bud Gall Midge
Rhopalomyia ericameriae is a gall midge in the family Cecidomyiidae, commonly known as the Rosette Bud Gall Midge. The species induces distinctive gall formations on host plants. As a member of the genus Rhopalomyia, it belongs to one of the most diverse genera of gall midges, with many species specialized on Asteraceae hosts.
Rhopalomyia erigerontis
Rhopalomyia erigerontis is a gall midge in the family Cecidomyiidae. It is known to induce galls on Erigeron (fleabane) species. The species was described by Felt in 1916. Like other members of its genus, it is associated with Asteraceae host plants.
Rhopalomyia obovata
Rhopalomyia obovata is a gall midge species in the family Cecidomyiidae, described by Gagné in 1983. The genus Rhopalomyia is one of the most diverse genera of gall midges, with many species inducing characteristic galls on various host plants. As with other members of this genus, R. obovata likely forms galls on specific host plant tissues, though detailed natural history information for this particular species appears limited in the available literature. The species is recognized as valid by GBIF and Catalogue of Life, with 266 observations recorded on iNaturalist.
Rhopalomyia sulcata
Rhopalomyia sulcata is a gall midge species in the family Cecidomyiidae, described by Raymond Gagné in 1995. As a member of the genus Rhopalomyia, this species is associated with inducing galls on host plants, though specific host associations for R. sulcata remain poorly documented. The genus is taxonomically diverse with many species specialized on particular plant genera, especially in the Asteraceae.
Rhopalomyia undescribed-species-on-amorpha
An undescribed species of gall midge in the genus Rhopalomyia that forms galls on Amorpha (false indigo), a genus of leguminous shrubs native to North America. As a member of Cecidomyiidae, this species likely exhibits the typical life cycle of gall midges with larval development occurring within plant tissue. The species remains formally undescribed in scientific literature, indicating it has been recognized by specialists but awaits formal taxonomic characterization. Its association with Amorpha suggests host-specificity, a common trait in Rhopalomyia species which often exhibit narrow host plant ranges.
Saperda populnea
small poplar borer
Saperda populnea is a longhorn beetle (Cerambycidae) that forms distinctive woody galls on twigs of poplars and willows. The species was described by Linnaeus in 1758 and has a broad distribution across the Northern Hemisphere. Females create characteristic horseshoe-shaped cuts on host twigs where eggs are deposited, leading to gall formation. The beetle is of economic concern in hybrid aspen plantations due to damage to young trees.
Smicronyx
seed weevils, sunflower seed weevils
Smicronyx is a large genus of true weevils (Curculionidae) containing over 220 described species distributed worldwide. Many species are specialized seed feeders, with several economically important members attacking cultivated sunflowers (Helianthus annuus) in North America. The genus includes gall-forming species and potential biological control agents for parasitic and invasive weeds. Larval development typically occurs within seeds or plant galls, with adults emerging to feed on pollen, buds, or foliage.
Sphenoptera jugoslavica
bronze knapweed root borer
Sphenoptera jugoslavica is a metallic wood-boring beetle in the family Buprestidae. It is monophagous on Centaurea diffusa (diffuse knapweed), forming spindle-shaped root galls in rosettes. The species is univoltine and was introduced to North America as a biological control agent for this invasive weed. Its effectiveness is limited by phenological requirements for arrested plant growth during oviposition.
Stephomyia
Stephomyia is a genus of gall midges in the family Cecidomyiidae, established by Tavares in 1916. The genus comprises seven described species distributed in the Neotropical region, with six species from South America and one (S. eugeniae) from North America. All species are gall-formers that induce plant galls on Myrtaceae hosts. A cladistic analysis based on morphological characters and host plant data supports the monophyly of the genus.
Taxodiomyia cupressi
Cypress Twig Gall Midge, Cypress Flower Gall Midge
Taxodiomyia cupressi is a gall midge (Diptera: Cecidomyiidae) that induces distinctive twig galls on cypress trees (Taxodium spp.). The species forms spongy, globular galls on new growth that are initially snow-white and turn brown with age. It has been documented in central Illinois and Missouri, with observations on cultivated bald cypress outside its native range. The midge undergoes complete metamorphosis with multiple generations per year, overwintering as larvae within fallen galls.
gall-midgeCecidomyiidaeTaxodiumbald-cypressgall-formerpestDipterainsectphytophagouscomplete-metamorphosismultiple-generationsoverwintering-larvaeornamental-pestriparianwetlandMissouriIllinoiscentral-USAtwig-gallspongy-gallwhite-gallbrown-gallexit-holesynchronized-emergencehost-specificTaxodiomyia-cupressiananassasynonymSchweinitz-1822Osten-Sacken-1878Taxodiomyia cupressiananassa
cypress twig gall midge
A gall midge in the family Cecidomyiidae that induces distinctive twig galls on cypress trees. The spongy galls are initially snow-white, turning brown with age, and eventually drop from the tree with leaf fall. Larvae pupate within the galls, with adults emerging later in the season or following spring. The species is considered a pest of ornamental and native cypress plantings.
Taxodiomyia taxodii
cypress leaf gall midge, cypress twig gall midge
A gall midge species in the family Cecidomyiidae that induces distinctive galls on cypress trees. Adults are tiny flies that lay eggs in cypress tissues, with larvae developing inside spongy, globular galls that initially appear snow-white and turn brown with age. The species is closely related to Taxodiomyia cupressiananassa, which produces similar galls on bald cypress.
Tephritidae
fruit flies, peacock flies
Tephritidae is a family of true fruit flies comprising nearly 5,000 described species across approximately 500 genera. Members are distinguished from Drosophilidae (also called fruit flies) by their larger size, patterned wings, and phytophagous larval biology. The family exhibits extraordinary morphological diversity, including elaborate wing markings that inspired the common name "peacock flies." Many species are economically significant agricultural pests, while others serve as biological control agents for invasive weeds. Taxonomy remains dynamic due to ongoing genetic and morphological revisions.
Tephritis
Tephritis is a large genus of true fruit flies (Diptera: Tephritidae) comprising approximately 170 described species, making it the sixth largest genus in the family. Species occur across diverse climate zones from hot semidesert to tundra, with the greatest diversity in the Palearctic region. Most species are associated with Asteraceae plants, inhabiting inflorescences of several tribes including Cardueae, Cichorieae, Anthemideae, Inuleae, and Senecioneae. Some species cause gall formation on host plants. The genus has been extensively studied for host-race formation and incipient speciation, particularly in T. conura and T. bardanae, which show genetic and morphological differentiation correlated with host-plant use.
Thecabius populimonilis
Bead-like Cottonwood Gall aphid
Thecabius populimonilis, commonly known as the Bead-like Cottonwood Gall aphid, is an aphid species in the family Aphididae. It induces distinctive galls on cottonwood trees (Populus species). The species exhibits a complex life cycle involving alternation between primary and secondary host plants.
Thecesternus hirsutus
bison dung weevil, bison snout beetle
Thecesternus hirsutus is a small, flightless weevil in the family Curculionidae, native to North America. It was first described by Pierce in 1909 and gained scientific attention through evaluation as a potential biological control agent for Parthenium hysterophorus in Australia. The species is nocturnal, spends winter as larvae underground feeding on plant roots, and is known for its cryptic appearance and death-feigning behavior when disturbed.
Tomoplagia
Tomoplagia is a genus of tephritid fruit flies (Diptera: Tephritidae) comprising approximately 60 described species. The genus is primarily Neotropical in distribution, with species recorded from Brazil and other South American regions. Larvae develop within plant tissues of Asteraceae, with documented associations including flower heads and stem galls on members of the tribe Vernonieae. Host specialization varies among species, ranging from monophagy to oligophagy on related host plants.
Trioza adventicia
syzygium leaf psyllid, lillypilly psyllid, eugenia psyllid
Trioza adventicia is a sap-sucking hemipteran in the family Triozidae that creates pit galls on leaves of Syzygium paniculatum. Native to eastern subcoastal Australia, this species has been introduced to California, southern Australia, and New Zealand where it affects ornamental plantings. For decades it was misidentified as Trioza eugeniae in scientific literature, horticultural resources, and biological control programs until a 2019 taxonomic revision using morphological and DNA barcoding evidence clarified the distinction. The biological control program in the United States unknowingly targeted the correct species despite the nomenclatural confusion.
Trioza brevigenae
Ficus leaf-rolling psyllid
Trioza brevigenae, known as the ficus leaf-rolling psyllid, is an invasive pest of Ficus microcarpa (Chinese banyan or Indian laurel fig) native to India. It was first detected in California in 2016, representing the first known occurrence outside its native range. The species causes characteristic leaf-roll galls on host foliage, with nymphs developing inside these protected structures. Its invasion pathway and full geographic distribution remain under investigation.
Trioza magnoliae
Red Bay Psyllid
Trioza magnoliae, commonly known as the Red Bay Psyllid, is a gall-forming psyllid native to eastern North America. This species induces characteristic galls on the leaves of native Persea bay trees, particularly red bay (Persea borbonia) and related species. The insect has a wide distribution across the eastern and central United States. While primarily an ecological curiosity due to its gall-forming habit, it has gained attention in relation to the decline of red bay populations caused by the invasive laurel wilt disease, as the psyllid's host trees face significant mortality.
Urophora affinis
Knapweed Gall Fly
Urophora affinis is a tephritid fruit fly native to Eurasia that was introduced to North America as a biological control agent for spotted knapweed (Centaurea maculosa) and diffuse knapweed (C. diffusa). The species forms galls in knapweed seed heads, where larvae develop and reduce seed production by up to 95%. First released in Montana in 1973, it has established populations but remains concentrated near release sites with limited dispersal ability. The fly is multivoltine, with adults emerging in June and larvae overwintering in seed heads.
Urophora cardui
Canada thistle gall fly, Thistle Stem Gall Fly
Urophora cardui is a tephritid fruit fly native to Central Europe, from the United Kingdom east to near the Crimea and from Sweden south to the Mediterranean. It has been introduced to North America as a biological control agent for Canada thistle (Cirsium arvense), an invasive weed. The species forms stem galls on its host plant and has been extensively studied for its population genetics, dispersal patterns, and interactions with parasitoids. Despite establishment in eastern Canada, its impact on host weed populations has remained limited.
Urophora jaceana
Urophora jaceana is a tephritid fruit fly that develops as a gall-former on knapweeds (Centaurea species). The species is native to Europe and has been introduced to eastern Canada. Its larvae induce galls in the flower heads of host plants, primarily black knapweed (Centaurea nigra) and Centaurea debeauxii.
Urophora quadrifasciata
Four-barred Knapweed Gall Fly
Urophora quadrifasciata is a tephritid fly native to Europe and parts of Asia, introduced to North America and Australia as a biological control agent for invasive knapweed species (Centaurea spp.). Larvae develop in flower heads of knapweeds, forming galls that reduce seed production. The species has become established in western North America following intentional releases in the early 1970s, though populations at some sites declined due to competition with the related Urophora affinis.
Walshia
Walshia is a genus of small moths in the family Cosmopterigidae, established by Clemens in 1864. The genus contains at least 12 described species distributed in North America. At least one species, W. amorphella, is known to induce galls on its host plant, creating complex ecological microcommunities. Most species remain poorly studied beyond basic taxonomic descriptions.
Walshia amorphella
Walshia amorphella is a small moth in the family Cosmopterigidae described by James Brackenridge Clemens in 1864. It is a gall-forming species that induces galls on the host plant Amorpha fruticosa. The species is known from the central United States, with records from Illinois, Iowa, Kentucky, Minnesota, Kansas, and Texas. Its gall-forming habit supports an associated microcommunity of other organisms.