If you read my posts last summer about the "top galls" to look for in 2023, you might recall some discussion of blister-like galls growing on the leaves of Silphium plants. These unassuming leaf swellings are quite unusual amongst Silphium gall wasps, especially given that most species induce only inconspicuous galls hidden within the host plant's tissues, and that the cauline leaves of most Silphium species are quick to shrivel up and break away during the growing season. You can see the original observation of the gall in Salina, Kansas on Silphium integrifolium: https://www.inaturalist.org/observations/167275394

I was fortunate enough to receive some samples of these galls from Ebony Murrell (@egmurrell) last year (more on her later on), and this week I was lucky enough to finally have adults to examine! To nobody's surprise, they are yet another undescribed gall wasp species, but perhaps more surprising is just how different they are from other species, both described and undescribed. An adult female of the new species is shown below and in the associated observation (https://www.inaturalist.org/observations/213220718).

All Silphium gall wasps are currently classified in the genus Antistrophus, a member of the herb gall wasp tribe Aulacideini. While there are 10 species currently classified in the genus (and an 11th on the way in an accepted manuscript of mine), these species are best classified in multiple genera on the basis of genetic and morphological data, and the Silphium gall wasps will become two independent genera. One genus is comprised of small-bodied, reddish gall wasps that primarily induce hidden galls in the stems (currently known as the rufus species complex), while the other genus is larger, black wasps that induce conspicuous galls on the apical stems and in the flowerheads. However, the species reared from the leaf blister galls doesn't resemble either of these putative genera well! As you can see in the below photos, this wasp has a deep red body, and is (relatively speaking) on the larger side of the Silphium wasp size spectrum. There are several differentiating characters on the mesosoma (=thorax in non-wasps), including the texture of the integument and the distinction of the notauli (the submedial line-like impressions) that are especially meaningful. Also interesting are some characters on the head and metasoma (=abdomen in non-wasps), including the protruding medial area on the face, the puncture patterns on the metasoma, and the surface texture of the head. Overall, the morphology of this new species suggests that it may best be classified in a separate genus. This distinction requires validation using genetic data, but this will come later on this summer.

Going further down the rabbit hole, these galls have also been observed on at least two additional Silphium species, S. gracile (https://www.inaturalist.org/observations/12082873) and S. cf radula (https://www.inaturalist.org/observations/165426473). Of course, the identity of the gall inducer on these other species is unknown. Could each Silphium species have its own blister gall wasp species? Or could one species be associated with each of these plants? Do other Silphium species have leaf blister gall wasps? And (the big ticket question) do these galls have any detrimental impacts on plant health like some of the other rosinweed gall wasps? Only further collection and rearing will enable investigation of these questions. Based on what I'm seeing in other Silphium gall wasps, I'm guessing these galls will eventually be discovered in most Silphium species, and each host plant species will have a specialist leaf galler. If you have Silphium species in your area, please consider checking the cauline leaves for unusual blister-like swellings like those shown in the above photos!

Lastly, I need to thank the excellent Ebony Murrell for her endless support in studying the gall communities of Silphium. She has gone above and beyond, and I'd like to think that our collaboration is turning her into a gall-obsessed maniac like the rest of us. She was the first person to bring these leaf blister galls to my attention, and kindly sent me many gall samples, including the gall that yielded the adult female photographed above. Ebony and the rest of The Land Institute (https://landinstitute.org/) have been incredibly supportive of my gall wasp studies, and we're currently devising plans to work on this exciting group of insects and their fantastic host plants.

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Hi everyone! For anyone that doesn't know me, I'm a fourth-year PhD candidate at Penn State, and part of my dissertation involves taxonomic work of several kinds on North American herb gall wasps. While many of you are likely familiar with cynipid wasp galls on oaks and roses, those on herbaceous plants are prevalent in most ecosystems but are greatly understudied. As a result, there are many species new to science to be found in North America!
In this post, I will highlight the Top 5 Herb Gall Wasps To Look For during this upcoming Gall Week (and beyond)! The fantastic iNaturalist community has sent me many specimens comprising many species (including many new to science!), and I’m once again reaching out to this platform to help me find even more species.
If you are willing to post observations of herb gall wasps or collect galls on my behalf, I would be greatly appreciative. Feel free to reach out to me with any questions! Commentary on collecting and rearing these gall wasps can be found in the post linked above.


Please note: This post is a greatly reduced version of a much larger, exhaustive post discussing North American herb gall wasps. If you're interested in my work or are excited about herb gall wasps, view the full post here: https://www.inaturalist.org/journal/louisnastasi/83741-north-american-herb-gall-wasps-what-we-know-so-far-and-what-is-still-needed

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#1: Rattlesnake Root Stem Cluster Gall (Aulacidea nabali)

Host plant(s): These galls have been reported on several species of rattlesnake roots (Nabalus): White rattlesnake root (Nabalus albus), tall rattlesnake root (Nabalus altissimus), nodding rattlesnake root (Nabalus crepideneus), and lion's foot rattlesnake root (Nabalus serpentarius).

Gall location: These galls are typically found at the base of the stem and often require some amount of excavation below the soil, although some reports indicate that the galls can be found higher up on the stem.

Distribution: These galls have been reported from various areas in the Eastern United States as well as southern Canada. It is likely that these galls might be found throughout the range of the host plants.

Comments: It is unclear whether galls induced on different rattlesnake root species correspond to a single gall wasp species, or multiple. Similarly, the presence of other gall types on rattlesnake roots is quite likely. Closely-related species of the genus Aulacidea induce several types of stem galls, including galls that leave no external sign of their presence (i.e., "cryptic" galls). These cryptic galls are quite possibly present on rattlesnake roots, and further sampling of these plants will almost certainly yield new species of gall wasps.

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#2: Desert-Chicory Stem Galls (Antistrophus sp.)

Host plant(s): These galls are known only on tuberous desert-chicory (Pyrrhopappus grandiflorus). Other species are likely hosts for this wasp or related species.

Gall location: These galls occur on the stem, forming large clusters or forming small spindle-like swellings.

Distribution: Thus far, these galls have been encountered in Oklahoma and Texas, but they likely occur elsewhere where the host plant is known.

Comments: This gall wasp, along with the following species, belongs to a group of gall wasps galling related plants in a subgroup of the lettuce tribe (Cichorieae: Microseridinae). These wasps appear to comprise a fairly diverse group, and many undescribed species likely exist on various other members of the subtribe Microseridinae.

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#3: Lindley's Silverpuff Stem Galls (Antistrophus spp.)

Host plant(s): These galls are found on Lindley's silverpuff (Uropappus lindleyi). Similar galls are found on other related host plants.

Gall location: These galls occur on the stem, forming nodular clusters or forming large spindle-like swellings (see above images for variation).

Distribution: California.

Comments: While there have been several observations of these galls on iNaturalist, the adult insects that induce these galls are unknown. It is unclear whether these are a known species or a species that is instead new to science. Similarly, it is unclear whether the two gall "types" are induced by one species or multiple. Interestingly, the large spindle-like swellings seem to occur at the base of the stem, while the cluster-like nodular galls occur higher up on the stems.

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#4: Rabbitbrush(?) Stem Galls (Antistrophus chrysothamni )

Host plant(s): When this species was described back in 1908, the host plant was reported as being a species of rabbitbrush in the genus Chrysothamnus. However, cynipid galls haven't been confirmed on this plant since, and only one series of specimens has been collected beyond those used to describe this species. As a result, the true host plant of this gall wasp is a mystery. There is a chance that the proper host is a species of Ericameria (formerly classified in Chrysothamnus, but this has yet to be examined closey.

Gall location: Somewhat large, ellipsoid galls can be found on the stems of the host plant.

Distribution: Arizona.

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#5: Rosinweed Leaf Blister Galls (Antistrophus spp.)

Host plant(s): These galls have been reported on several species of rosinweeds, namely slender rosinweed (S. gracile), whole-leaf rosinweed (S. integrifolium), and rough-stem rosinweed (S. radula). Other rosinweed species are also likely hosts for these galls.

Gall location: These wasps induce distinct, blister-like galls along the leaf veins, often on leaves low on the plant.

Distribution: These galls have been reported in Kansas, Arkansas, and Texas so far, but these galls likely exist throughout the possible range of rosinweed plants in North America.

Comments: Gall wasps associated with rosinweeds (Silphium) represent one of the more diverse gall wasp lineages associated with a single plant genus, comprising at least 14 known species. The leaf blister galls represent at least one species new to science, although each rosinweed species probably hosts a unique gall wasp species based on trends seen in other rosinweed gall wasps. Galls on rosinweed also occur on the terminal stems, lower stems, hidden within the stem (i.e., cryptic galls), hidden within the leaf petioles, and in the flowers. We've only extensively sampled a handful of rosinweed species in the Midwestern US, but the more than 20 additional species likely host a tremendous diversity of unknown gall wasps.

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Hi all! It's been a while since I've sent out a large update on Aulacideini in North America, and with Gall Week this coming week, there’s no better time to provide an update. For anyone that doesn't know me, I'm a fourth-year PhD candidate at Penn State, and part of my dissertation involves taxonomic work of several kinds on North American herb gall wasps. In this post, I'll provide an overview of knowledge on these insects, as well as some key targets that require more observation and collection. The fantastic iNaturalist community has sent me many specimens comprising many species (including many new to science!), and I’m once again reaching out to this platform to help me find even more species.

This is a long and fairly exhaustive post, but each section includes distribution data so you can easily search for species that might occur in your area. For a more detail-oriented treatment of these insects, check out my recent open-access (=free download) field guide, although it's somewhat outdated only 10 months later.

At the end of this post is a list of key targets for collection this year! Please do examine this list and see which species you might be able to find in your area.

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Contents

Click on the section names below to go to that section!

Section 1: Introduction

Section 2: Microseridinae Gall Wasps

Section 3: Lettuce Gall Wasps

Section 4: Silphium Gall Wasps

Section 5: Hawkweed Gall Wasps

Section 6: Other Assorted Gall Wasps

Collecting and Rearing Herb Gall Wasps

Key Targets for Collection

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Introduction

Many of you are likely familiar with oak galls induced by wasps of the tribe Cynipini. However, gall wasps induce galls on a vast array of host plants, and those other than oak gall wasps have not received much study in recent years (or ever!). My focus is on gall wasps associated with herbaceous plants (i.e., often short lived plants that are not trees or shrubs). In North America, cynipid galls on herbaceous plants are induced by species belonging to three tribes: Aulacideini (my primary focus), Diastrophini (these primarily gall Rubus and Potentilla), and Phanacidini (two known species, both introduced from Europe).

As published in my recent catalogue of North American gall wasps, there are 21 species of the tribe Aulacideini known in North America. However, very early on in my study, it was immediately obvious that our current knowledge only scratched the surface. Thus far, I've encountered as many as 50 total species of Aulacideini in North America, many of which are undescribed species (i.e., new to science) that I intend to describe. In addition to many new species, the two genera of Aulacideini present in North America (Antistrophus and Aulacidea) are polyphyletic, meaning that they contain species representing several different lineages that are not closely related. Because of this, many species of North American herb gall wasps will need to be moved to new genera that will be established as a result of my studies. All in all, there are clearly many classification problems in this group that I am aiming to resolve with my studies.

This post will be split into several sections based on the host plant taxon. Each section will begin with a table outlining the known gall wasps on that host taxon, including the following information:

1. Species name
2. An representative observation of a gall (hyperlinked to the species name)
3. Distribution
4. Host plant species
5. Plant organ galled
6. A brief description of the gall's shape or general appearance
7. Whether I have successfully acquired adults of that species (which are needed to describe or redescribe a species)
8. Whether I have successfully sequenced the DNA of that species (mighty helpful in describing a species)

Please peruse this list to learn about progress on my research, and what material you might be able to collect to help understand the biodiversity of this group of insects! If you have any questions about these insects, or galls and wasps in general, do feel free to comment below or message me otherwise! At the end of the post, I have included some information on collecting and rearing herb gall wasps if you'd be so kind as to collect some material on my behalf. Anything listed in this post as not sequenced or without adults known is of high priority for collection!

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Microseridinae Gall Wasps

The species in this group all induce galls on a subgroup of the lettuce tribe (Asteraceae: Cichorieae: Microseridinae). These wasps appear to form a monophyletic group (i.e., a “good group” that contains an ancestor and all of its descendants) and appear to comprise three true genera.

Species	Distribution	Host plant	Galled organ	Gall shape	Adults?	Sequenced?
Antistrophus pisum	Midwestern and Western US + adjacent Canada	Lygodesmia juncea	Stems	Pea-shaped	Yes	Yes
Antistrophus sp. nov.	Midwestern and Western US + adjacent Canada	Lygodesmia juncea	Stems	Spindle	Yes	Yes
Antistrophus sp. nov.	Midwestern and Western US + adjacent Canada	Lygodesmia juncea	Basal stems (usually below soil!)	Amorphous	Yes	Yes
Antistrophus microseris	California; one record from Arizona	Microseris douglasii	Stems	Spindle	Yes	Yes
Antistrophus sp. nov.?	California	Microseris paludosa	Stems	Spindle	No	No
Antistrophus sp. nov.	Southcentral US; Texas and Oklahoma	Pyrrhopappus grandiflorus	Stems	Cluster/spindle	Yes	Yes
Antistrophus sp. nov.?	California	Uropappus lindleyi	Stems	Cluster/spindle	No	No

Gall wasps on plants belonging to the Microseridinae appear to comprise a fairly diverse group. It is likely that undescribed species exist on other species of Microseris (of which there are many), as well as other genera in this group such as Agoseris. There are also several additional species of Lygodesmia in the Midwestern and Southern US that could be hosts for undescribed gall wasps.

At this time, it is unclear whether galls found on Microseris paludosa and Uropappus lindleyi are new host plant records for Antistrophus microseris or if these galls truly represent new species. Given the restrictive host plant range of most herb gall wasps, it is quite likely that these are new species, but DNA sequences and examination of adult wasps would be necessary to confirm this.

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Lettuce Gall Wasps

Species in this group all belong to the genus Aulacidea, the most diverse herb gall wasp genus comprising more than 40 species known in North America and Eurasia. Aulacidea is in desperate need of reclassification, as the vast majority of species classified here do not belong. In fact, only the species of gall wasps classified in Group B are properly classified in this genus!

Species	Distribution	Host plant	Galled organ	Gall shape	Adults?	Sequenced?
Aulacidea podagrae	Widespread in Eastern and Midwestern US	Lactuca biennis	Stems	Variable; cluster- or node-like	Yes	Yes
Aulacidea sp. nov.	Widespread in Eastern US	Lactuca biennis	Stems	Cryptic cells hidden in stem tissue	Yes	Yes
Aulacidea abdita	Eastern US and Canada?	Lactuca canadensis???	Stems	Cryptic cells hidden in stem tissue	Yes	No
Aulacidea harringtoni	Widespread in Eastern and Midwestern US	Lactuca canadensis	Stems	Cryptic cells hidden in stem tissue	Yes	Yes
Aulacidea tumida	Widespread in Eastern and Midwestern US	Lactuca canadensis	Stems	Variable; usually clavate or spindle-like	Yes	Yes

The lettuce gall wasps comprise several species of host-specific wasps that induce either visible or cryptic (hidden) galls. Thus far, I have confirmed the identity of lettuce gall wasps on only two species of lettuce, Canadian lettuce (Lactuca candensis) and tall blue lettuce (L. biennis), although there are several other lettuce species in North America.

Several species in this group have uncertain host affiliations. Aulacidea abdita was described by Alfred C. Kinsey in 1920 from adults dissected from old stems that he considered to be Canadian lettuce. Unfortunately, his specimens were greatly damaged (the stems were over 40 years old by the time he dissected them!), but several characters of the head and wings make this species distinct enough. I have not yet encountered this species amongst material my collaborators and I have reared, and I am rather doubtful that Canadian lettuce is the correct host plant for this species. Similarly, we have found galls resembling Aulacidea podagrae on Florida lettuce (Lactuca floridana), but the identity of the inducer remains unclear.

Overall, collecting material from more lettuce species is essential in understanding the biodiversity of these insects, and will help us better understand which plants are used by which wasps. At this time, it seems that only native lettuce species are galled by cynipid wasps.

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Silphium Gall Wasps

This group is by far the most diverse group of Aulacideini in North America. Species associated with plants of the genus Silphium were originally found on just four Silphium species, but we’ve found many new species and many new host plants since the last major studies of the group. Species in the below table are grouped based on the location and type of gall they induce.

Species	Distribution	Host plant	Galled organ	Gall shape	Adults?	Sequenced?
Flower Gall Wasps (Antistrophus laciniatus species complex)	Apparently widespread in Eastern, Midwestern, and Southern US		Flowers	Kernel-shaped galls, solitary or clustered, often hidden in disc flower
Antistrophus bicolor		Silphium integrifolium			Yes	Yes
Antistrophus laciniatus		Silphium albiflorum, S. laciniatum, S. terebinthinaceum			Yes	Yes
Antistrophus sp. nov.		Silphium perfoliatum			Yes	Yes
Antistrophus sp. nov.?		Silphium gracile			Only a few old adults from museum collections	No
Globular Stem Gall Wasps	Apparently widespread in Eastern, Midwestern, and Southern US		Stems	Large, round to clustered swellings
Antistrophus silphii		Silphium asteriscus var. trifoliatum, S. compositum, S. gracile, S. integrifolium, S. perfoliatum, S. radula	Apical stems	Large round galls, often at tips of short stems	Yes	Yes
Antistrophus sp. nov.		Silphium integrifolium	Lower stems	Clustered galls, on middle or lower stems	Females only!	No
Antistrophus sp. nov.		Silphium perfoliatum	Lower stems	Clustered galls, on middle or lower stems	Males only!	No
Cryptic Gall Wasps	Apparently widespread in Eastern, Midwestern, and Southern US			Cryptic cells hidden within tissue
Antistrophus jeanae		Silphium perfoliatum	Stems		Yes	Yes
Antistrophus meganae		Silphium terebinthinaceum; also hybrids of S. terebinthinaceum and S. laciniatum	Stems		Yes	Yes
Antistrophus minor		Silphium laciniatum	Stems		Yes	Yes
Antistrophus rufus		Silphium laciniatum	Stems		Yes	Yes
Antistrophus sp. nov.		Silphium laciniatum, S. terebinthinaceum	Leaf veins and petioles		Yes	Yes
Antistrophus sp. nov.		Silphium asteriscus var. trifoliatum	Stems		Yes	Yes
Antistrophus sp. nov.		Silphium dentatum	Stems		Yes	Yes
Antistrophus sp. nov.		Silphium integrifolium	Stems		Yes	Yes
Leaf Blister Gall Wasps — unsure how many species, but all undescribed!	Apparently widespread in Eastern, Midwestern, and Southern US	Silphium gracile, integrifolium, radula	Leaf membrane along midrib	Large blisters in leaf tissue, most apparent on underside of leaf	No	No

Comprising at least 14 species, Silphium gall wasps represent one of the most diverse gall wasp communities associated with a single plant genus, behind those on oaks and roses. Given the uncertain status of several species (especially those inducing leaf blister galls), further sampling of Silphium is essential within further understanding the diversity of these insects. Brock and Weakley’s 2020 treatment of Silphium recognizes 27 species and varieties, and thus far we’ve only sampled a handful for the presence of cynipid galls. The remaining ~20 Silphium taxa are almost certainly hosting a tremendous diversity of gall wasps, and there are almost certainly undiscovered gall morphotypes. Our sampling has focused on the Midwestern Silphium, but species in the Southeast and Southcentral United States are prime targets for further sampling.
Interestingly, the vast majority of Silphium gall wasps are specialists on a single host plant. Each species of Silphium gall wasp likely occurs throughout the range of its respective host plant(s), although it’s unclear whether all Silphium populations are capable of sustaining gall wasps. It seems that the wasps prefer large, native populations, although prairie restorations are also frequently found to contain galls.

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Hawkweed Gall Wasps

Species	Distribution	Host plant	Galled organ	Gall shape	Adults?	Sequenced?
Aulacidea hieracii	Great Lakes area	Hieracium umbellatum and possibly other Hieracium	Stems	Fusiform to clavate	Yes (but more would be good!)	Yes (but more would be good!)
Aulacidea pilosellae	Canada?	Pilosella spp.	Leaves	Blister	No	No
Aulacidea subterminalis	US & Canada?	Pilosella spp.	Stolons	Elliptical to clustered	No	No
Aulacidea sp. nov.	California (only one record so far)	Hieracium albiflorum	Leaves	Blister	No	Yes (from dissected larvae)

Several species of herb gall wasps induce galls on true hawkweeds (Hieracium) and mouse-eared hawkweeds (Pilosella). Two of these species have been introduced as control agents for invasive plants, and it’s unclear whether the other species are native or represent introduced populations.
I recently found the first known galls of a species inducing leaf galls on Hieracium albiflorum in California! Thus far, I have been able to sequence the larvae of this gall wasp, but we have not yet been able to rear adult insects, which would be necessary to describe this species.
It’s quite likely that more species in this group exist, as we have not heavily sampled hawkweeds in North America. Searching prominent native species such as rattlesnakeweed (H. venosum) would be a great way to find potential new species.

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Other Assorted Gall Wasps

Species	Distribution	Host plant	Galled organ	Gall shape	Adults?	Sequenced?
Aulacidea acroptilonica	Pacific Northwest	Rhaponticum repens (this species has been classified in many genera over time)	Stems	Fusiform to clustered	Yes	Yes
Aulacidea sp. nov.	California	Unknown!	Unknown!	Unknown!	Yes (only old museum material)	No
Aulacidea nabali	Widespread in Eastern and Midwestern US and Canada	Nabalus spp.	Lower stems, often below soil line	Elliptical to clustered	Yes (only old museum material)	No
Antistrophus chrysothamni	Arizona	Chrysothamnus???	Stems	Elliptical to clavate	Yes (only old museum material)	No
Liposthenes glechomae	Widespread	Glechoma hederacea	Stems and leaves	Blister-like to elliptical	Yes	Yes

These taxa are those that don’t fit neatly into another category and represent several different lineages. Several of these species are poorly characterized, known only from a small series of museum specimens, and one new species is known entirely from four female specimens collected in California.

In the case of Antistrophus chrysothamni, the species was first described in 1908, and it has been nearly a century since a valid record has been taken. The species was originally described as galling Chrysothamnus, but no galls matching those of this wasp have since been found on these plants. As a result, it is unclear what the true host plant is for this species, and acquiring new material would be essential in understanding the biology and classification of Antistrophus chrysothamni.

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Collecting and Rearing Herb Gall Wasps

Collecting herb gall wasp galls is the most rewarding way to study these insects. Collecting and rearing a single gall will likely yield a great diversity of insects, including the offspring of the gall inducer as well as parasitoids and other gall inhabitants.

Many herb gall wasps induce what are called “cryptic” galls , meaning they induce galls that are not discernable based on external changes to the plant tissue. The widespread presence of cryptic galls has likely greatly contributed to our lack of knowledge about these insects due to the inherent challenges in locating and sampling them. Cryptic galls are best located by finding a large population of a potential host plant and dissecting a series of stems. Stems containing cryptic galls will likely display numerous oval-shaped chambers within the stem tissue as well as numerous larvae inhabiting the chambers. Once you’ve confirmed the presence of cryptic galls, you should collect entire stems of that plant. You can cut them into pieces to store and rear them (see remarks in the following paragraphs). In most cases, the base of the stem is the most densely populated part of the stem, so you should be sure to collect the entire above-ground part of the stem when sampling for cryptic galls.

The following excerpt from our Field Guide to Herb and Bramble Gall Wasps of North America provides an overview for collecting cynipid galls. If you have any questions about collecting or rearing these galls, please do not hesitate to contact me!

“Collecting and rearing a gall is perhaps the best way to verify its identity. Adult gall-inducing insects can provide a wide breadth of data related to galls. Luckily, herb and bramble galls are relatively easy to collect and rear, especially in comparison to oak galls.
Herb and bramble galls should be collected starting in the late Fall, ideally after the first frost of the season has occurred, and can be collected up until the emergence period of the residing insects (late Spring through Summer). For galls on herbaceous plants, it is usually best to collect them after the host plant has senesced; doing so ensures that the larvae developing inside the gall have had plenty of time to mature and feed on the gall tissue.
Rearing these galls (that is, successfully obtaining adult insects from a field-collected gall) is rather straightforward. Galls should be placed in a rearing container like a disposable plastic cup or zip bag. Air holes that are small enough so as to prevent the escape of emerging insects should be poked to prevent the growth of mold. Additionally, they need to be stored somewhere that allows exposure to natural climate fluctuations similar to those of their natural habitats. The authors of this guide recommend that, if possible, galls be left in an open-air shed without climate control. Galls may also be stored in a tight-fitting bin or container provided that they are allowed to expe- rience temperature fluctuations and mold growth is prevented.
You might notice that gall wasps are not the only insects to emerge from galls. Many other insects, especially parasitoid wasps, exploit the shelter and resources of existing galls to feed their own young; these insects are often reared from galls instead of, or alongside, the true gall inducers.
Insects reared from galls can be preserved by storing them in alcohol (ideally 90- 95% ethanol) or by mounting them; there are many useful resources for insect preservation that may be consulted for information on this process.”

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Key Collection Targets

Key collection targets are organized into three groups: known species that require further sampling, a list of host plants that are likely to host gall wasps, and a list of plant genera that are more speculative in their possible role as gall wasp hosts. Use the following hyperlinks to navigate these lists:

List of Known Gall Wasps to Look For

List of Likely New Host Plants

List of Speculative Host Plant Genera

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List of Known Gall Wasps to Look For

The species in this list are known species that require more study before description or re-description.

Genus and species	Host plant	Host organ galled	Distribution
Antistrophus spp.	Silphium spp.	Leaves (blister galls)	Widespread
Antistrophus chrysothamni	Chrysothamnus?	Stems	Arizona
Antistrophus laciniatus	Silphium albiflorum (I have sequence data for other known hosts already)	Flowers	Texas
Antistrophus sp. nov.?	Microseris paludosa	Stems	California
Antistrophus sp. nov.?	Uropappus lindleyi	Stems	California
Aulacidea nabali	Nabalus spp.	Lower stems (often below soil)	Widespread in Eastern US and adjacent Canada
Aulacidea sp. nov.	Hieracium albiflorum (possibly other species too)	Leaves (blister galls)	California; probably more widespread

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List of Likely New Host Plants

The plant species listed in this table belong to genera that host gall wasps, but gall wasps have yet to be found on these specific species. Given the host use trends of known species, it is quite likely that these plants host gall wasps (and probably species new to science) given that other species in their genera are hosts.

Family	Genus and species	Distribution	Possible galled plant parts
Asteraceae	Hieracium	Widespread in US and Canada	Stems, stolons, and leaves
	Hieracium abscissum	Southwestern US and Mexico
	Hieracium argutum	California
	Hieracium bolanderi	Southwestern US and Baja California (Mex.)
	Hieracium brevipilum	Southwestern US
	Hieracium carneum	Southwestern US and Chihuahua (Mex.)
	Hieracium crepidispermum	Southwestern US and Mexico
	Hieracium fendleri	Southern US and Mexico
	Hieracium greenei	Pacific Northwest
	Hieracium gronovii	Eastern North America
	Hieracium horridum	Pacific Northwest & Nevada
	Hieracium longiberbe	Pacific Northwest
	Hieracium longipilum	Central US and Canada
	Hieracium megacephalon	Southeastern US
	Hieracium nudicaule	Pacific Northwest
	Hieracium paniculatum	Eastern North America
	Hieracium parryi	Pacific Northwest
	Hieracium pringlei	Southwestern US
	Hieracium robinsonii	Far North (Maine, New Hampshire, and adjacent Canada)
	Hieracium scabrum	Eastern North America
	Hieracium schultzii	Texas and Mexico
	Hieracium scouleri	Northwestern North America
	Hieracium traillii	Appalachian and Mid-Atlantic US
	Hieracium triste	Western US
	Hieracium venosum	Eastern North America
	Hieracium vulgatum	Northern North America
Asteraceae	Lactuca	Widespread in US and southern Canada	Only stem galls known (both cryptic and visible galls) but other organs may have undiscovered galls
	Lactuca floridana	Widespread
	Lactuca graminifolia	Southern US
	Lactuca hirsuta	Widespread
	Lactuca ludoviciana	Southern and Midwestern US
Asteraceae	Lygodesmia	Widespread in Western US; also Florida and Georgia	Stems (both upper stems and basal stems below soil)
	Lygodesmia aphylla	Florida and Georgia
	Lygodesmia grandiflora	Western North America
	Lygodesmia ramosissima	Texas and Mexico
	Lygodesmia texana	Southcentral US and Mexico
Asteraceae	Microseris	Western North America, mostly West Cost	Stems
	Microseris acuminata	West Coast
	Microseris bigelovii	West Coast
	Microseris borealis	West Coast up to Alaska
	Microseris campestris	California
	Microseris elegans	California
	Microseris howelii	Oregon
	Microseris laciniata	West Coast
	Microseris nutans	Widespread in Western US and Canada
	Microseris sylvatica	California
Asteraceae	Pyrrhopappus	Widespread in Eastern and Central US	Stems
	Pyrrhopappus carolinianus	Eastern and Central US
	Pyrrhopappus pauciflorus	Texas and Mexico
	Pyrrhopappus rothrockii	Arizona, New Mexico, and Texas
Asteraceae	Silphium	US and parts of southern Canada	Stems, flowers, leaves (both cryptic and visible galls)
	Silphium albiflorum	Texas
	Silphium asperrimum	Southcentral and Southeastern US
	Silphium asteriscus (and varieties)	Southeastern US
	Silphium brachiatum	Southeastern US
	Silphium compositum (and varieties)	Southeastern US
	Silphium confertifolium	Alabama
	Silphium connatum	Mid-Atlantic US (VA, WV, NC)
	Silphium dentatum	Southeastern US
	Silphium glutinosum	Bibb County, Alabama
	Silphium gracile	Southcentral US
	Silphium mohrii	Appalachian US
	Silphium perplexum	Alabama
	Silphium pinnatifidum	Appalachian and Southcentral US
	Silphium radula	Southcentral US
	Silphium reniforme	Southeastern US
	Silphium simpsonii	Southeastern US
	Silphium speciosum	Lower Midwestern US
	Silphium wasiotense	Appalachian US

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List of Speculative Host Plant Genera

The plant genera listed in this table might host gall wasps based on relatedness to taxa already known to host gall wasps. These taxa are much more speculative than those in the above table, but may prove to be hosts of notable gall wasp diversity.

Plant Genus	Distribution
Subtribe Crepidinae (2 genera listed here; this tribe includes Nabalus which has a known gall wasp)	Widespread in North America
Crepis (Several native spp. worth checking)	Widespread in North America
Taraxacum (Several native spp. worth checking)	Widespread in North America
Subtribe Microseridinae (18 genera listed)	Primarily western North America
Agoseris (11 spp.)	Western North America
Agoseris (11 spp.)	Western North America
Anisocoma (1 sp. – A. acaulis)	Southwestern US
Atrichoseris (1 sp. – A. platyphylla)	Southwestern US and Northwestern Mexico
Calycoseris (2 spp.)	Southwestern US and Northwestern Mexico
Chaetadelpha (1 sp. – C. wheeleri)	Southwestern US
Glyptopleura (2 spp.)	Southwestern US
Krigia (7 spp.)	Eastern North America
Malacothrix (18 spp.)	Western US and Northwestern Mexico
Marshalljohnstonia (1 sp. – M. gypsophila)	Coahuila, Mexico
Munzothamnus (1 sp. – M. blairii)	California
Nothocalais (4 spp.)	Western and Central North America
Pinaropappus (2 US spp.)	Southern US and most of Mexico
Pleiacanthus (1 sp. – P. spinosus)	Western US
Prenanthella (1 sp. – P. exigua)	Southwestern US
Rafinesquia (2 spp.)	Southwestern US
Shinnersoseris (1 sp. – S. rostrata)	Central North America
Stephanomeria (14 spp.)	Western North America

Hello everyone!

Some time ago, I began developing plans for a course dedicated to teaching identification of wasps to students, amateurs, and others who would benefit from practical knowledge of the insect order Hymenoptera. After many months of collaboration between myself and over twenty contributors, I am pleased to announce that as of today, registration for the WaspID Course is now open to all who are interested! We are all very excited for this opportunity to engage all communities through this celebration of wasps and all that makes them unique and worthy of study.
The course will run over the first two weeks of January 2022 and is designed to allow for asynchronous participation in core course material. The course has been developed with students, amateurs, and nature enthusiasts in mind! Course details and registration links are available on our WordPress site here: www.WaspIDCourse.WordPress.com
Please let me know if you have any questions or concerns!

Thanks everyone!

Louis Nastasi