The reference shelf

Three swellings on a stem

Three insects swell a goldenrod stem, and their galls overlap enough in size that shape alone will not tell you which is which. The exit hole will. Only the elliptical gall is plugged, with a pale bung set flush in the wall.

Who carries what

Every host on the left, every gall form across. A handful of goldenrods carry almost everything; most carry one gall or none. Solidago altissima alone accounts for more than a fifth of all records here.

If you are holding a stem

Not a substitute for a real key. Three facts you can observe will usually get you to a short list.

The words

This guide uses about 45 words that do a lot of work in entomology and almost none anywhere else. Most are underlined where they appear, and say what they mean when you hover or focus them. They are all here too.

gall

A growth an insect or fungus makes a plant build, and then lives inside. Every cell of it is the plant's own; the occupant supplies the instructions.

gall inducer

The organism that causes the gall, as opposed to the many that move in afterwards.

bivoltine

Two generations in a year.

univoltine

One generation in a year.

multivoltine

More than two generations in a year.

instar

The stage between two moults. A third-instar larva has moulted twice.

oviposit

To lay an egg.

ovipositor

The tube a female insect lays eggs through; in the parasitoid wasps here it has to reach through the gall wall.

parasitoid

An insect whose larva develops on or inside a single host and kills it. A parasite, by contrast, does not.

inquiline

A lodger: an insect that develops inside a gall it did not induce.

host race

A population living and mating on one host plant, partly cut off from populations on other hosts.

parthenogenetic

Developing from an unfertilised egg.

thelytokous

Parthenogenetic, and producing only daughters: no males.

ptilinum

A balloon-like sac a young fly inflates on its head to force its way out; it collapses afterwards and leaves a seam on the face.

cytokinin

A plant hormone that drives cell division.

auxin

A plant hormone that drives cell elongation and growth.

monothalamous

Single-chambered: one larva inside.

polythalamous

Many-chambered.

mycelium

The thread-like body of a fungus.

apical

At the tip. The apical bud is the growing point at the top of a stem.

petiole

The stalk that joins a leaf to the stem.

midrib

The central vein running the length of a leaf.

rhizome

An underground stem that a plant spreads and overwinters by.

ramet

One shoot of a clonal plant. A goldenrod clump spreading by rhizome may be a single genetic individual.

capitulum

The flower head of a daisy-family plant: many small florets packed into what reads as one flower.

floret

One of the many true flowers inside a daisy-family head. The outer ray florets each carry a single strap; the inner disc florets are tubular.

phyllaries

The small overlapping bracts forming the cup beneath a flower head.

involucre

The whole cup of phyllaries around the base of a flower head.

secund

All turned to one side. In goldenrods the heads sit along the upper surface of an arching branch, and it is the most useful single character in the genus.

corymbiform

Flat-topped. The lower stalks are the longest, so every head finishes at about the same height.

paniculiform

A branched spray: the flowering branches branch again, widest at the bottom and tapering upward into a rough pyramid.

thyrsiform

Dense, narrow and tall: short side branches packed close around one upright axis, so it reads as a club or a wand rather than a spray.

racemiform

Heads carried singly on their own short stalks along one unbranched axis, like beads set down a stem.

virgate

Wand-like: long, slender, straight, and hardly branched.

glabrate

Nearly hairless, or losing its hairs as it ages.

strigose

With stiff straight hairs lying flat against the surface, all pointing the same way.

strigillose

Finely strigose: the same flattened hairs, smaller and sparser.

villous

With long, soft, shaggy hairs.

bracteate

Bearing bracts, small reduced leaves along the flowering branches, where a full leaf would be too big.

bracteole

A very small bract, on the stalk of a single flower head rather than at a branch.

fusiform

Spindle-shaped, widest in the middle, tapering to both ends.

glaucous

With a bluish-grey waxy bloom.

pubescent

Finely hairy.

tephritid

A member of Tephritidae, the picture-winged fruit flies.

cecidomyiid

A member of Cecidomyiidae, the gall midges.

Photographs

Every photograph on this guide was taken by somebody else and is used under the licence they chose. 175 photographs from 138 observers, hotlinked from iNaturalist; the images are theirs, not this guide's, and each links back to the observation it came from. 54 of them are the goldenrods themselves, and appear when you hover a plant's name; 64 are the caterpillars.

Sources

Every work here is cited with its actual authors. Five entries carried "(authorship unconfirmed)" until the papers themselves were tracked down on 2026-08-02.

The catalogue itself rests on a body of revisionary taxonomy that the prose does not quote directly: the Dasineura work and its evidence for host-associated differentiation,2829 the world catalogue of Cecidomyiidae,31 and Felt's 1917 key,47 which is where a great deal of this began and where several of the still-unnamed galls were first noticed.

Three more come from the recording's own works cited, and were run down afterwards: the two field guides whose way of sorting goldenrods by the shape of the flowering top is used on the plant page,5253 and Daniel McClosky's photographic catalogue of goldenrod galls, which is the closest thing to this guide that already existed.57

1. 1Michalek, B. & Jones, S. (The Field Guides) (2015). Episode 01: Goldenrod Galls, recorded 20 September 2015 at Hunters Creek Park, Erie County, New York. linkcited in↩The galls · Rhopalomyia solidaginis · Gnorimoschema gallaesolidaginis · About
2. 2Gallformers Contributors (2026). Gallformers.org — host associations, gall traits and identification notes. Data CC BY-NC-SA 4.0. linkcited in↩The galls · Eurosta solidaginis · Rhopalomyia solidaginis · Asteromyia carbonifera · Procecidochares atra · Rhopalomyia capitata · Eutreta novaeboracensis · The plant · Reference · About
3. 3iNaturalist (2026). Observation counts, retrieved via the iNaturalist API. linkcited in↩The caterpillars · Reference · About
4. 4McClosky, D. (iNaturalist: ddennism) (2019–2023). Goldenrod Galls; Goldenrod Leaf Bunch Galls; Stem Galls on Goldenrods (and friends): Gnorimoschema Moth Galls. iNaturalist journal, three posts. A sourced catalogue of goldenrod gall-inducers. linkcited in↩The galls · Rhopalomyia solidaginis · Procecidochares atra
5. 5Dorchin, N., McEvoy, M. V., Dowling, T. A., Abrahamson, W. G. & Moore, J. G. (2009). Revision of the goldenrod-galling Rhopalomyia species (Diptera: Cecidomyiidae) in North America. Zootaxa 2152: 1–35. linkcited in↩The galls · Rhopalomyia solidaginis · Rhopalomyia capitata · Eutreta novaeboracensis
6. 6Gagné, R. J. (1989). The Plant-Feeding Gall Midges of North America. Cornell University Press.cited in↩Asteromyia carbonifera
7. 7Abrahamson, W. G. & Weis, A. E. (1997). Evolutionary Ecology across Three Trophic Levels: Goldenrods, Gallmakers, and Natural Enemies. Princeton University Press.cited in↩Eurosta solidaginis
8. 8Weis, A. E. & Abrahamson, W. G. (1994). Variable selection on Eurosta's gall size. II. A path analysis of the ecological factors behind selection. Evolution 48: 734–745. linkcited in↩Eurosta solidaginis
9. 9Abrahamson, W. G. (Bucknell University) (n.d.). The Solidago–Eurosta Gall research resource. linkcited in↩Eurosta solidaginis · Reference · About
10. 10Mapes, C. C. & Davies, P. J. (2001). Cytokinins in the ball gall of Solidago altissima and in the gall-forming larvae of Eurosta solidaginis. New Phytologist 151: 203–212. linkcited in↩The galls · Eurosta solidaginis
11. 11Ponce, G. E., Fuse, M., Chan, A. & Connor, E. F. (2021). The localization of phytohormones within the gall-inducing insect Eurosta solidaginis (Diptera: Tephritidae). Arthropod-Plant Interactions 15: 375–385. linkcited in↩Eurosta solidaginis
12. 12Fiutek, N., Couger, M. B., Pirro, S., Roy, S. W., de la Torre, J. R. & Connor, E. F. (2023). Genomic assessment of the contribution of the Wolbachia endosymbiont of Eurosta solidaginis to gall induction. International Journal of Molecular Sciences 24: 9613. linkcited in↩Eurosta solidaginis
13. 13Storey Lab, Carleton University (n.d.). Cell and molecular responses to stress: goldenrod gall fly and goldenrod gall moth. linkcited in↩Eurosta solidaginis
14. 14Levis, N. A., Yi, S.-X. & Lee, R. E., Jr (2012). Mild desiccation rapidly increases freeze tolerance of the goldenrod gall fly, Eurosta solidaginis: evidence for drought-induced rapid cold-hardening. Journal of Experimental Biology 215: 3768–3773. linkcited in↩Eurosta solidaginis
15. 15Miller, W. E. (2000). A comparative taxonomic–natural history study of eight Nearctic species of Gnorimoschema that induce stem galls on Asteraceae. linkcited in↩The galls · Gnorimoschema gallaesolidaginis · The caterpillars · About
16. 16Miller, W. E. (1977). Biology and taxonomy of three gall-forming species of Epiblema (Olethreutidae). linkcited in↩Epiblema scudderiana · The caterpillars
17. 17Zhang, G., Storey, J. M. & Storey, K. B. (2017). Elevated chaperone proteins are a feature of winter freeze avoidance by larvae of the goldenrod gall moth, Epiblema scudderiana. Journal of Insect Physiology 106: 106–113. linkcited in↩Epiblema scudderiana
18. 18Rickards, J., Kelleher, M. J. & Storey, K. B. (1987). Strategies of freeze avoidance in larvae of the goldenrod gall moth, Epiblema scudderiana: winter profiles of a natural population. Journal of Insect Physiology 33: 443–450. linkcited in↩Epiblema scudderiana
19. 19Storey, K. B. & Storey, J. M. (2012). Insect cold hardiness: metabolic, gene, and protein adaptation. Canadian Journal of Zoology 90: 456–475. linkcited in↩Epiblema scudderiana
20. 20Storey, J. M. & Storey, K. B. (2004). Cold hardiness and freeze tolerance. In: Functional Metabolism: Regulation and Adaptation (K. B. Storey, ed.), ch. 17, pp. 473–503. Wiley-Liss. linkcited in↩Epiblema scudderiana
21. 21Churchill, T. A. & Storey, K. B. (1989). Metabolic correlates to glycerol biosynthesis in a freeze-avoiding insect, Epiblema scudderiana. Journal of Comparative Physiology B 159: 461–472. linkcited in↩Epiblema scudderiana
22. 22Heath, J. J. & Stireman, J. O. (2010). Dissecting the association between a gall midge, Asteromyia carbonifera, and its symbiotic fungus, Botryosphaeria dothidea. Entomologia Experimentalis et Applicata. linkcited in↩Asteromyia carbonifera · About
23. 23Stireman, J. O., Devlin, H., Carr, T. G. & Abbot, P. (2010). Evolutionary diversification of the gall midge genus Asteromyia (Cecidomyiidae) in a multitrophic ecological context. Molecular Phylogenetics and Evolution 54: 194–210. linkcited in↩Asteromyia carbonifera
24. 24Gagné, R. J. (1968). A taxonomic revision of the genus Asteromyia (Diptera: Cecidomyiidae). linkcited in↩Asteromyia carbonifera
25. 25Plakidas, J. D. (2016). The Gall Midges (Diptera: Cecidomyiidae: Cecidomyiinae) from Allegheny County, Pennsylvania. linkcited in↩Asteromyia carbonifera
26. 26Baine, Q., Casares, E. E., Carabotta, E., Martinson, V. G. & Martinson, E. O. (2023). Galls on galls: a hypergall-inducing midge and its parasitoid community. Ecology 104: e4018. linkcited in↩The galls · Rhopalomyia capitata
27. 27Dorchin, N., Joy, J. B., Hilke, L. K., Wise, M. J. & Abrahamson, W. G. (2015). Taxonomy and phylogeny of the Asphondylia species (Diptera: Cecidomyiidae) of North American goldenrods. Zoological Journal of the Linnean Society 174: 265–304. linkcited in↩The galls · Asphondylia
28. 28Dorchin, N., Clarkin, C. E., Scott, E. R., Luongo, M. P. & Abrahamson, W. G. (2007). Taxonomy, life history, and population sex ratios of North American Dasineura (Diptera: Cecidomyiidae) on goldenrods. linkcited in↩Rhopalomyia capitata · Reference
29. 29Dorchin, N., Scott, E. R., Clarkin, C. E., Luongo, M. P., Jordan, S. & Abrahamson, W. G. (2009). Behavioural, morphological, ecological and genetic evidence for host-associated differentiation in the gall midge Dasineura folliculi on two sympatric goldenrods. linkcited in↩Reference
30. 30Eiseman, C. S. (2024). Procecidochares atra Loew (Tephritidae) and Rhopalomyia capitata Felt (Cecidomyiidae) reared from single-chambered rosette galls on rough-stemmed goldenrod (Solidago rugosa). Proceedings of the Entomological Society of Washington 125(2): 273–277. linkcited in↩The galls · Rhopalomyia solidaginis · Rhopalomyia capitata
31. 31Gagné, R. J. & Jaschhof, M. (2021). A Catalog of the Cecidomyiidae (Diptera) of the World, 5th edition. linkcited in↩Reference
32. 32National Wildlife Federation (n.d.). Keystone Native Plants: Eastern Temperate Forests, Ecoregion 8. Lepidoptera host data from D. W. Tallamy and the University of Delaware; specialist-bee host data from J. Fowler. linkcited in↩The plant · The caterpillars · About
33. 33Narango, D. L., Tallamy, D. W. & Shropshire, K. J. (2020). Few keystone plant genera support the majority of Lepidoptera species. Nature Communications 11: 5751. linkcited in↩The caterpillars
34. 34Wise, M. J., Abrahamson, W. G. & Cole, J. A. (2010). The role of nodding stems in the goldenrod-gall-fly interaction: a test of the “ducking” hypothesis. American Journal of Botany 97(3): 525–529. linkcited in↩The galls
35. 35Messina, F. J. (1981). Plant protection as a consequence of an ant–membracid mutualism: interactions on goldenrod (Solidago sp.). Ecology 62: 1433–1440. linkcited in↩The galls
36. 36Morales, M. A., Barone, J. L. & Henry, C. S. (2008). Acoustic alarm signalling facilitates predator protection of treehoppers by mutualist ant bodyguards. Proceedings of the Royal Society B 275: 1935–1941. linkcited in↩The galls
37. 37Cunan, E. T., et al. (2015). Evidence for plant-mediated competition between defoliating and gall-forming specialists attacking Solidago altissima. American Midland Naturalist 173: 208–217. linkcited in↩The galls
38. 38Parker, E. G., Dobson, K. C., Young, M. L., Hammond, M. D. & Zarnetske, P. L. (2026). Climate warming and drought modify galling effects on tall goldenrod. Oecologia 208: 51. linkcited in↩Rhopalomyia solidaginis
39. 39Hartnett, D. C. & Abrahamson, W. G. (1979). The effects of stem gall insects on life history patterns in Solidago canadensis. Ecology 60: 910–917. linkcited in↩Eurosta solidaginis
40. 40Stoltzfus, W. B. (1977). The biology and taxonomy of Eutreta (Diptera: Tephritidae). linkcited in↩Eutreta novaeboracensis · About
41. 41Philips, T. K. & Smith, D. C. (1998). The biology and hosts of Procecidochares atra (Diptera: Tephritidae): evidence for cryptic species? Entomological News 109: 159–164. linkcited in↩Procecidochares atra
42. 42Aldrich, J. M. (1929). A revision of the two-winged flies of the genus Procecidochares in North America. Proceedings of the United States National Museum 76(2799): 1–13. linkcited in↩Procecidochares atra
43. 43Novak, J. A. & Foote, B. A. (1980). Biology and immature stages of fruit flies: the genus Eurosta (Diptera: Tephritidae). Journal of the Kansas Entomological Society 53: 205–219. linkcited in↩The galls · About
44. 44Sutton, B. D., Steck, G. J. & DeFoe, D. (2002). New records of Tephritidae (Diptera) from Great Smoky Mountains National Park — II. Insecta Mundi 16(1–3): 1–8. linkcited in↩The galls
45. 45Eastman, J. A. (2003). The Book of Field and Roadside. Stackpole Books. linkcited in↩The galls
46. 46Stokes, D. (1976). A Guide to Nature in Winter. Little, Brown and Company.cited in↩Eurosta solidaginis
47. 47Felt, E. P. (1917). Key to American Insect Galls. New York State Museum Bulletin 200. linkcited in↩Reference · About
48. 48Semple, J. C. & Cook, R. E. (2006). Solidago. In: Flora of North America north of Mexico, vol. 20. Oxford University Press. Consulted via eFloras.org. linkcited in↩The galls · The plant · About
49. 49Semple, J. C. & Beck, J. B. (2021). Revised infrageneric classification of Solidago (Asteraceae: Astereae). Phytoneuron 2021-10: 1–6, read in full. The species total (about 140 worldwide) and the intuitive-phylogeny branching order are from the authors' University of Waterloo Astereae Lab pages and Semple & Beck 2023 (Phytoneuron 2023-41: 1–5), whose phylogeny figure is © J. C. Semple and is not reproduced. linkcited in↩The plant
50. 50Semple, J. C., McMinn-Sauder, H., Stover, M., Lemmon, A. R., Lemmon, E. M. & Beck, J. B. (2023). Goldenrod herbariomics: hybrid-sequence capture reveals the phylogeny of Solidago (Asteraceae: Astereae). American Journal of Botany 110(7): e16164. A phylogenomic tree of the diploid goldenrods, hundreds of loci deep; the molecular backbone the intuitive branching order this guide's tree follows is built on. The figure is not reproduced here. linkcited in↩The plant
51. 51Weakley, A. S. & the Southeastern Flora Team (2026). Flora of the Southeastern United States. University of North Carolina Herbarium, North Carolina Botanical Garden. Web edition. linkcited in↩The plant · About
52. 52Peterson, R. T. & McKenny, M. (1996). A Field Guide to Wildflowers: Northeastern and North-central North America. Houghton Mifflin. (First published 1968.)cited in↩The plant · Reference
53. 53Newcomb, L. (1977). Newcomb's Wildflower Guide. Little, Brown and Company.cited in↩The plant · Reference
54. 54Merriam-Webster (n.d.). Euthamia, in Merriam-Webster.com Dictionary. linkcited in↩The plant
55. 55Ojibwe People's Dictionary (n.d.). A searchable, talking Ojibwe–English dictionary. Department of American Indian Studies, University of Minnesota. Entries consulted: giizis (sun, moon, a month) and mashkiki (medicine). linkcited in↩The plant
56. 56Lee, M. (2022). Giizisomashkiki: Goldenrod (Solidago). AANIIN WAABIGWANIIN: hello, flowers! Episode of 27 December 2022. linkcited in↩The plant
57. 57McClosky, D. (2019). Goldenrod galls: a photographic catalogue. iNaturalist journal. linkcited in↩Reference
58. 58Britton, N. L. & Brown, A. (1913). An Illustrated Flora of the Northern United States, Canada and the British Possessions, 2nd ed. Public domain. linkcited in↩About
59. 59Comstock, J. H. & Comstock, A. B. (1895). A Manual for the Study of Insects. Comstock Publishing Company, Ithaca. The round goldenrod gall is Fig. 593, p. 486, where the ball gall is named Trypeta solidaginis and the elliptical gall Gelechia gallaesolidaginis. Public domain. linkcited in↩The galls · Gnorimoschema gallaesolidaginis
60. 60Riley, C. V. (1869). The Solidago gall moth — Gelechia gallaesolidaginis, n. sp. In: First Annual Report on the Noxious, Beneficial and Other Insects of the State of Missouri, Plate II, figs. 1–2. Public domain. linkcited in↩Gnorimoschema gallaesolidaginis
61. 61Root, R. B., Loeffler, C. C. & Rawlins, J. E. (2024). Trends in the traits, functions, and affinities of caterpillars (Lepidoptera) associated with goldenrod (Solidago altissima). Annals of Carnegie Museum 88(4): 321–350. linkcited in↩Epiblema scudderiana · Gnorimoschema gallaesolidaginis · The caterpillars
62. 62Clemens, B. (1859). Contributions to American lepidopterology. Reprinted in: The Tineina of North America, ed. H. T. Stainton, 1872, p. 81. Public domain. linkcited in↩The caterpillars
63. 63Braun, A. F. (1925). Some undescribed Microlepidoptera and notes on life histories. Transactions of the American Entomological Society 51: 13–24. Public domain. linkcited in↩The caterpillars