Be on the Look Out: Pussytoe-Pineapples

by Bryan England* and Carol Ann McCormick^ *Preserve Manager, Annie Louise Wilkerson, MD Nature Preserve, City of Raleigh, NC ^Curatrix, University of North Carolina at Chapel Hill Herbarium (NCU) ORCID: 0000-0003-3785-8433

Be On the Look Out — It’s Pussytoe Pineapple season again!

Pussytoes (Antennaria spp.) aren’t necessarily rare plants (although two species are on the North Carolina Natural Heritage Program’s “Watch List”), but Pussytoe “Pineapples” seem to qualify as a rare “plant phenomenon.” The “pineapples” are the products of a tiny gall-midge fly (Asphondylia antennariae), originally described from Wisconsin by entomologist William Morton Wheeler in 1889. The “pineapple” encloses a single larva, which pupates inside.

“Insects can reprogram plant growth, transforming ordinary plant parts into intricately patterned shelters that are safe havens for feeding and reproduction. These structures, called galls, have fascinated biologists for centuries. They’re crafted by a variety of insects, including some species of aphids, mites and wasps. And they take on innumerable forms, each specific in shape and size to the insect species that’s created it — from knobs to cone-shaped protrusions to long, thin spikes. Some even resemble flowers.”1

In the case of the insect Asphondylia antennariae, it transforms the bud tissue of the pussytoe into a structure resembling a pineapple. Since 1889, this distinctive gall has been reported from only a handful of mid-western and north-eastern states – never from any southeastern state.

“During the spring months of 1888 and 1889 I observed that the plantlets of Antennaria plantaginifolia covering a sloping pasture in an open wood near St. Francis, Milwaukee [Wisconsin], had been so severely attacked by Cecidomyids as to have had almost all their terminal buds converted to galls. As the plant infested is only a weed and the flies consequently of no agricultural interest, I at first determined to leave undescribed the two new species which I have reared from the galls, but careful examination of the larvae during pupation convinced me that I had found a subject which would reward careful morphological study, especially as there was no lack of material. I shall probably publish at some future time the results of my investigations on the tissue changes accompanying metamorphosis, and for this reason have concluded to describe the two new species… The galls [of the two new species] are easily confounded at first sight… More careful examination, however, soon reveals enough differences to permit of distinguishing the two species.“2

Wheeler goes on to describe Cecidomya antennariae and Asynapta antennariae. It is Wheeler’s second species, now called Asphondylia antennariae, which we recently recognized occurring on wild Antennaria in Raleigh.

“The [Asphondylia ] gall is more elongate, while the tips of the component leaves are scarcely recurved. The development of white trichomes [hairs] is more regular, giving the gall a satiny appearance. The inner or upper surface of the leaves do not produce [hairs] as in the other gall, but are smooth and shing, and are found to be covered with minute drops of moisture when the leaves are stripped assunder… Each gall contains only a single insect, which is not swathed in woolly trichomes but hollows out for itself a smooth cavity with hard and nut-like walls… The dark-colored fly emerges at the apex of the gall after dragging out its pupa case, which is left dangling among the woolly hairs on the outer surface of the leaves. The insect hops and flits about … in a lively manner.“2

Wheeler then goes on to describe the male and female gall midges in detail, including behavioral traits.

“The males ran about over the leaves in the jar to which they were confined in pursuit of the females. They seldom used their wings but seemed to rely from progression almost exclusively on their long and delicate legs. Whenever one approached a female, she rose into the air and alighted some distance off. I have repeatedly observed this coquettish action which had every appearance of being a test of the ardor and agility of the male, as with higher animals. Further studies of the habits of such of our insects as present striking sexual differences will undoubtably reveal many cases of courtship, no less wonderful than those observed in birds.“2

Annie Louise Wilkerson, MD Nature Preserve staff Sophia Boyd and Bryan England first noticed the pussytoe galls in North Raleigh several years ago, but at that time there were no recent publications available describing them. However since then, a paper by Charles S. Eiseman has appeared with nice photos from New York matching our North Carolina “pineapple” specimens.3

Does the arrival of Pussytoe-Pineapple Gall Midge have implications for plant conservation in North Carolina? According to Wheeler (1889), he observed these gall-flies produced “terrible ravages” on the Antennaria in Wisconsin. In fact, Wheeler said “The severe ravages of the gall fly would undoubtedly result in the extermination of Antennaria plantaginifolia, at least in some localities, were it not that it is itself much infested by a minute Proctotrupid [parasitic micro-wasp].” So here at the Wilkerson Nature Preserve we’ve kept an eye on them for the last few years, even though our Antennaria are merely the common A. plantaginifolia (in the broad sense). However, it is concerning that the recent specimens found in New York by Eiseman were believed to come from A. neglecta , one of our NC “Watch List” pussytoe species.3

Because Antennaria are somewhat toxic to deer, they are one of the last native herbaceous species surviving in our “deer desert” forests which have lost most herbaceous cover. We’d hate to lose them too. We have seen a lot of “pineapples”, but fortunately the galls here don’t always seem fatal to our plants. Perhaps they are mostly harmless to our species. And the Antennaria within the Wilkerson Nature Preserve’s annual-fire-maintained, deer-excluded areas don’t seem to get the galls at all.

As a conservation issue, we’d like to know how rare are Pussytoe-Pineapple Gall Midges really? Dr. Ray Gagné, a gall-midge specialist at the Smithsonian, reportedly said in 2020 that he had never before seen these galls, not in a 50+ year gall-focused career.4 “Research grade” sightings (see iNaturalist map below) in the last couple years do seem to be increasing across the northern United States. Wilkerson Nature Preserve in Wake County was the first observation in North Carolina.

“It is thought that the Cecidomyiidae [gall midges] comprise more species than any other insect family, with the total number exceeding that of the entire order Coleoptera [beetles]. Given this diversity, the group is severely understudied, with only 6651 species having been described as of 2021… It is inevitable that any naturalist studying plants will notice and wonder about cecidomyiid galls…”3

If you notice and wonder about “Pussytoe Pineapples” this fall, please take note — perhaps you will find a new location for the insect! The galls are very obvious right now – you’ll notice the “pineapples” right away if you find a patch of Antennaria hosting the gall midge. Join other Community Scientists and submit your observations of Pussytoe-Pineapple Galls to iNaturalist. As herbaria also support entomological research, pressed plant specimens bearing galls from Wilkerson Nature Preserve are now being prepared by Wilkerson Preserve staff. Those will be deposited in the University of North Carolina at Chapel Hill Herbarium.

“Pineapple” structure made by Pussytoe in response to the gall-midge laying an egg in the plant tissue. “Asphondylia antennariae galls are not supposed to have leaves that are recurved at the tips, but this turns out not to be a consistent difference,” according to Charles Eiseman.4 Photo by Bryan England

POSTSCRIPT // FAST-BREAKING PUSSYTOE-PINEAPPLE NEWS: Bryan England sent out the information about Pussytoe-Pineapples to the North Carolina Rare Plant Listserv at 9:38am on 23 September, 2026. That email was the foundation for this newsletter article. Within hours, naturalists were posting to the listserv about about their encounters with the galls caused by Asphondylia antennariae.

Dr. Tracy Feldman, Assistant Manager of the Durant Nature Preserve about 3 miles from Wilkerson Nature Preserve, saw Bryan England’s email, and immediately searched Durant Preserve for “pineapples”. He found some. Dr. Feldman also found an older photo of a pussytoe from Durant that showed a pineapple which had not been previously recognized. By the end of the day he’d added those observations to iNaturalist.

Gemma Milly, botanist with Virginia Natural Heritage Program, sent this to the listserv at 4:29pm on 23 September, 2026: “This is so interesting, thanks for sharing it, Bryan. I adore the name and stopped during errands at an opportune and new-to-me parking lot in suburban Richmond, Virginia today to peek at what looked like a good bank of liverworts, algae and such, and I was happy to find two pussytoe pineapples, in a population of probably 500-1000 plants. Surely, they must be common. Literally the first place I encountered after reading your email, in rando spot eastern North America and there they were, possibly a state record, that easy? Survey n=1, but hey. I’ve certainly seen these things before over the years — I couldn’t say where in the eastern United States — and while some part of my brain thought they looked like an interesting gall, another resolved the thought with an explanation that they are a normal, occasional part of wild pussytoe populations, not to concern myself with — we all have to draw a line somewhere … (For some reason my line has included liverworts and excluded midge galls, except this one now.) Undoubtedly I’m not the only one who has passed these many times without second thought.”

Bryan England replied to Ms. Milly: “Gemma — Congratulations on finding (possibly the first? wow!) Pussytoe Pineapple from the Commonwealth of Virginia! To answer your question, from just the external gall appearance, I can’t be completely certain your galls are the same Asphondylia antennariae as mine. There is another Pussytoe Pineapple gall midge, Rhopalomyia antennariae. If you opened the gall and found the larva/pupa then you could tell them apart without much trouble. Asphondylia antennariae has a solitary larva/pupa in each gall (monothalamous) – but Rhopalomyia antennariae will normally have multiple larva inside the galled area (polythalamous). We know…almost nothing…about these insects in the Southeast. You may find some are parasitized by micro-wasps. Those wasps do not even have formal scientific names. There’s just so many unknown little invertebrates all around us all the time! So I completely hear what you’re saying about “we all have to draw a line somewhere”. For me, being a conservation botanist first, I draw my line when an insect seems to have potential to negatively impact a plant. Not just by taking a little nibble, but by being seemingly able to thwart a plant’s life cycle. Then I’ll investigate. Maybe it will turn out to be harmless, but with rare plants, and other plants with small populations, I like to know what’s out there that might be capable of having an impact. For plants on the edge, every additional bit of mortality counts. But every naturalist can “draw their lines” differently! It is so interesting that you found 2 “pineapples” out of 500-1000 plants. These gall-midges can become MUCH denser than that (the “terrible ravages” Wheeler described). [I found] a patch where ~50% of the plants seem to be galled. Are galled stems able to flower the following spring? I’m not sure that they are.”

To read more about insect galls, I recommend you read: Aishwarya Korgaonkar, Clair Han, Andrew L. Lemire, Igor Siwanowicz, Djawed Bennouna, Rachel Kopec, Peter Andolfatto, Shuji Shigenobu, and David L. Stern. “A novel family of secreted insect proteins linked to plant gall development.” Current Biology. Published online March 2, 2021. Doi: 10.1016/j.cub.2021.01.104

1. Hamers, Laurel. 2021. Here’s how insects coax plants into making galls. HHMI / Janelia Research Campus Blog. https://www.janelia.org/news/heres-how-insects-coax-plants-into-making-galls accessed on 23 September 2026.

2. Wheeler, William M. 1889. On two new species of Cecidomyid flies producing galls on Antennaria plantaginifolia. Proceedings of the Wisconsin Natural History Society. https://babel.hathitrust.org/cgi/pt?id=hvd.32044107187411&seq=3

3. Eiseman, Charles S. 2024. Miscellaneous records of the Cecidomyiidae (Diptera) from the USA. Proceedings of the Entomological Society of Washington 126(4): 454-473. https://www.researchgate.net/profile/Charles-Eiseman/publication/390978034_Miscellaneous_Records_of_Cecidomyiidae_Diptera_from_the_USA/links/680789a6d1054b0207dc0fd6/Miscellaneous-Records-of-Cecidomyiidae-Diptera-from-the-USA.pdf

4. Eiseman, Charles S. 2020. A Peculiar Patch of Pussytoes. BugTracks blog of January 29, 2020. https://bugtracks.wordpress.com/2020/01/29/a-peculiar-patch-of-pussytoes/ accessed on 24 September 2026.