Antistrophus chrysothamni

Aulacidea hieracii

Aulacidea subterminalis

Phanacis hypochoeridis

Aulacidea abdita

Aulacidea harringtoni

Aulacidea podagrae

Aulacidea tumida

Aulacidea annulata

Antistrophus l-juncea-collar-gall

Antistrophus pisum

Antistrophus l-juncea-spindle-gall

Antistrophus microseris

Aulacidea nabali

Antistrophus p-pauciflorus-stem-blister

Aulacidea acroptilonica

Antistrophus laciniatus

Antistrophus s-gracile-flower-gall

Antistrophus s-integrifolium-flower-gall

Antistrophus rufus

Antistrophus minor

Antistrophus jeanae

Antistrophus meganae

Antistrophus laurenae

Antistrophus s-dentatum-cryptic-stem-gall

Antistrophus s-astericus-cryptic-stem-gall

Antistrophus silphii

Antistrophus s-perfoliatum-stem-swelling

Antistrophus s-laciniatum-cryptic-leaf-gall

Phanacis taraxaci

Liposthenes glechomae

Diastrophus fragariae

Diastrophus fusiformans

Diastrophus niger

Diastrophus potentillae

Diastrophus tumefactus

Diastrophus bassettii

Diastrophus cuscutaeformis

Diastrophus kincaidii

Diastrophus nebulosus

Diastrophus radicum

Diastrophus turgidus

Aulacidea ambrosiaecola

Unknown d-lactea-stem-swelling

Diastrophus p-congesta-stem-gall

Unknown r-trivialis-stem-gall

Unknown rubus-like-d-rosae

Antistrophus m-lindleyi-basal-stem-gall

Unknown s-perfoliatum-stem-cluster

Antistrophus chrysothamni
Rabbitbrush gall wasp

Host: An as-of-yet unidentified species of rabbitbrush. 

Gall location: Found on the branches, sometimes with several galls on the same branch. 

Description: Rounded, medium-sized galls that are 1-3 centimeters in length and containing many chambers. Externally, they are covered in dense, white, felt-like hairs. Internally, they are white and pithy. 

Range: Only known from two places in Arizona: Tucson and Cave Creek. 

This species has not been seen in nearly a century! It was originally described by William Beutenmüller in 1908, and since then it has been seen only once, by Lewis H. Weld in the 1920s. The exact rabbitbrush species was not known when this gall wasp was first described. Many rabbitbrush species that are found in Arizona have a large range and can be found in many nearby states, so it is possible that this gall wasp may be encountered elsewhere in the southwestern United States

Aulacidea hieracii
Canada hawkweed stem gall wasp

Host: Canada hawkweed (Hieracium umbellatum). 

Gall location: On the stem, often near the apex but sometimes developing further down. 

Description: Rounded, fleshy, medium-sized galls, usually 1-3 centimeters in length. Sometimes with abundant soft, pale hairs, but sometimes entirely without hairs. Green when fresh to brown when old and dry. 

Range: In North America, this species may be found in several North Central US states including Minnesota and Wisconsin as well as adjacent parts of Canada including Manitoba and Ontario. 

This species has apparently been introduced, but its only known host plant in North America, Canada hawkweed, is indeed native to both Europe and North America. As a result, it is unclear whether this species was truly introduced or is native in its current range. Complicating this question further is the unclear taxonomy of this species; it is possibly a complex of multiple closely-related species that each prefer a different species of hawkweed. In Europe, where this species is native, it induces galls on several hawkweed species. Overall, further research is necessary to substantiate the identity of the North American population. 

Similarly, the subterminal hawkweed gall wasp (Aulacidea subterminalis) may also have been introduced to North America. Its galls apparently occur on the stolons rather than on the main stem. However, like the Canada hawkweed stem gall wasp, its status in North America is unclear.

Similarly, the subterminal hawkweed gall wasp (Aulacidea subterminalis) may also have been introduced to North America. Its galls apparently occur on the stolons rather than on the main stem. However, like the Canada hawkweed stem gall wasp, its status in North America is unclear.

Phanacis hypochoeridis
Catsear stem gall wasp

Host: Catsear (Hypochaeris radicata). 

Gall location: On the stem, typically midway down the length of the stem. 

Description: Elongate, spindle-shaped swellings containing many chambers, often 1-5 centimeters in length. Green and fleshy when fresh to brown and dry when old. 

Range: This species is primarily known in North America from the West Coast, particularly California, Oregon, and British Columbia. A small population has apparently been identified in North Carolina. 

This species was introduced to North America from Europe along with its host plant. Catsear occurs throughout most of the United States and some parts of Canada, so the gall may occur in additional states not listed above. The catsear gall wasp and the dandelion gall wasp (Phanacis taraxaci), both of which are introduced species, are the only representatives of the gall wasp tribe Phanacidini to be found in North America.

Aulacidea abdita
Cryptic lettuce stem gall wasp [same entry applied to [A harringtoni](https://www.gallformers.org/gall/1431)]

Hosts: Biennial lettuce (Lactuca biennis), Canada lettuce (L. canadensis), Florida lettuce (L. floridana), and possibly prairie lettuce (L. ludoviciana).

Gall location and description: Galls of these species are cryptic, meaning they are not outwardly visible and can only be located upon dissection of a galled stem. When dissected, the stem will have numerous brown, rounded chambers along the inside of the pith, each with a single insect. 

Range: These galls are primarily known from the Northeastern United States and adjacent areas of Canada, from Ontario south to North Carolina and west to Oklahoma, but they are likely under-reported and may probably be found throughout the United States and Canada within the range of their host plants. 

These species have unclear taxonomy and may be synonymous or may instead be composed of multiple true species, but each of the hosts listed above is believed to host cryptic galls induced by gall wasps of the genus Aulacidea. Museum specimens identified by Alfred C. Kinsey indicate that these galls may also occur in stems of prairie lettuce (L. ludoviciana), but the authors of this guide have yet to substantiate this claim.

Aulacidea harringtoni
Cryptic lettuce stem gall wasp [same entry applied to [A abdita](https://www.gallformers.org/gall/1432)]

Hosts: Biennial lettuce (Lactuca biennis), Canada lettuce (L. canadensis), Florida lettuce (L. floridana), and possibly prairie lettuce (L. ludoviciana).

Gall location and description: Galls of these species are cryptic, meaning they are not outwardly visible and can only be located upon dissection of a galled stem. When dissected, the stem will have numerous brown, rounded chambers along the inside of the pith, each with a single insect. 

Range: These galls are primarily known from the Northeastern United States and adjacent areas of Canada, from Ontario south to North Carolina and west to Oklahoma, but they are likely under-reported and may probably be found throughout the United States and Canada within the range of their host plants. 

These species have unclear taxonomy and may be synonymous or may instead be composed of multiple true species, but each of the hosts listed above is believed to host cryptic galls induced by gall wasps of the genus Aulacidea. Museum specimens identified by Alfred C. Kinsey indicate that these galls may also occur in stems of prairie lettuce (L. ludoviciana), but the authors of this guide have yet to substantiate this claim.

Aulacidea podagrae
Lettuce node gall wasp

Hosts: Biennial lettuce (Lactuca biennis) and Florida lettuce (L. floridana). 

Gall location: These galls occur throughout the stem, occasionally in multiple disjunct areas. 

Description: Highly variable. Generally present as lumpy, amorphous galls jutting outwardly from the stem. Sometimes, they appear as smaller, more-isolated galls rather than larger, more-confluent swellings. They may be single-chambered or have many chambers depending on the individual gall’s shape, size, and structure. Usually brown and rough outwardly with fleshy green areas between apparent nodes. 

Range: This gall is known throughout the Eastern United States, from Pennsylvania south to Virginia and west to Kansas. It is likely underreported and probably occurs in additional areas. 

This species was originally described in association with Canada lettuce (Lactuca canadensis), but despite substantial recent sampling, it has only been successfully found on biennial lettuce (L. biennis) and Florida lettuce (L. floridana). The original description does mention that the host plant may have been misidentified, further enabling this possibility. The wasps inducing galls on Florida lettuce may prove to be a species distinct from those on biennial lettuce as there are some differences in gall appearance between the two host plants.

Aulacidea tumida
Lettuce tumor gall wasp

Hosts: Canada lettuce (Lactuca canadensis) and possibly prairie lettuce (L. ludoviciana). 

Gall location: On the stem, often toward the apex but occasionally further down on the stem. 

Description: Extremely variable. The most common appearance for these galls is as large, 3-5 centimeters in diameter, round, and many-chambered, sometimes baring leaves and branches. Occasionally, they are more spindle-shaped, or instead appear as smaller galls, barely-swollen and gnarled. Green and fleshy when fresh to brown and rough when old and dry. 

Range: The known range for this species is from southern Quebec south to Virginia and west to Minnesota and Arkansas. 

Due to the tremendous variability of this gall, its taxonomy is rather uncertain. Another described species, Aulacidea annulata, is almost certainly a synonym of A. tumida; Aulacidea annulata is currently associated with the spindle-shaped, irregular galls, but ongoing taxonomic studies will likely validate this synonymy in the near future. Similarly to the cryptic lettuce stem gall wasps, museum specimens indicate that the Canada lettuce stem gall wasp may also occur on prairie lettuce (L. ludoviciana), but this claim remains unsubstantiated

Another described species, Aulacidea annulata, is almost certainly a synonym of A. tumida; Aulacidea annulata is currently associated with the spindle-shaped, irregular galls, but ongoing taxonomic studies will likely validate this synonymy in the near future. 

Antistrophus sp.
Skeletonplant collar gall wasp

Host: Rush skeletonplant (Lygodesmia juncea). 

Gall location: On the collar of the stem, often just above or just below where the stem meets the soil. You may need to clear the soil around the base of the stem to find this gall, as its location often puts it below the soil line. 

Description: Typically present as a cluster of several round, single-chambered galls, each less than a centimeter in width, around the collar. Rarely, only one or two galls are present. Green or yellowish and fleshy when fresh to brown and rough when old and dry. 

Range: This gall has only been reported from Manitoba and Nebraska thus far, but its range probably matches that of the skeletonplant pea gall wasp (see next species). 

This gall is induced by an undescribed species of the genus Antistrophus. This species was originally assumed to be a variant of the skeletonplant pea gall wasp, but preliminary results from an ongoing taxonomic study indicate that they are indeed different species. Galls of this species occur only on the main stem, unlike the other two species of gall wasps known from skeletonplant which occur only on the branches

Antistrophus pisum
Skeletonplant pea gall wasp

Host: Rush skeletonplant (Lygodesmia juncea). 

Gall location: On the branches, often in large numbers on the same plant. 

Description: These galls are small, ranging greatly in size from roughly 0.3-1.5 centimeters in diameter, and distinctly pea-shaped. Fresh galls are green and fleshy, and older galls are brown, dry, and rough. The galls develop on the outside of the branch rather than being directly integrated into the branch tissue. 

Range: The established range for this species includes much of the Central United States and adjacent areas of Canada, from Manitoba south to Texas and west to Alberta. 

The skeletonplant pea gall wasp is likely even more widespread within the range of its host plant, which is known from British Columbia south to southern California and east to Minnesota and Texas. This species has often been referred to as Antistrophus lygodesmiaepisum, but Antistrophus pisum is the most correct scientific name for the skeletonplant pea gall wasp. Specimens of this species have been mistakenly reported from several other host plants, including baccharis (Baccharis spp.) and wirelettuce (Stephanomeria spp.), but galls of this species only occur on rush skeletonplant.

Antistrophus sp.
Skeletonplant spindle gall wasp

Host: Rush skeletonplant (Lygodesmia juncea). 

Gall location: On the branches. 

Description: Similar in appearance to galls of the skeletonplant pea gall wasp, but unlike that species, galls of the skeletonplant spindle gall wasp are directly integrated into the branch tissue. Overall, these galls are spindle-shaped swellings of the branches, often around 1 centimeter in length. Green and fleshy when fresh to brown and rough when dry and old. 

Range: Thus far, this gall has only been located in several Midwestern states as well as southern Manitoba. However, as with the skeletonplant pea gall wasp, its range is probably far greater than currently known. 

This gall is induced by an undescribed species of the genus Antistrophus. As with the skeletonplant collar gall wasp, this species was originally assumed to be a variant of the skeletonplant pea gall wasp, but preliminary results from an ongoing taxonomic study indicate that they are indeed different species.

Antistrophus microseris
Silverpuff stem gall wasp

Host: Douglas’ silverpuff (Microseris douglasii). 

Gall location: On the stem, typically at or above the middle. 

Description: These galls are medium-sized, spindle-shaped, rounded swellings of the stems, typically 1-3 centimeters in diameter. Fresh galls are green and fleshy, and older galls are brownish, and rough. Internally, mature galls contain several brown “dividers” that are believed to be constructed by the gall wasp larvae during development; the exact process leading to the development of these dividers is unknown. 

Range: This species has only been reported from California. However, this gall has been poorly studied, and likely occurs on other silverpuff species, which could increase the possible range of this gall throughout the Western United States. Similarly, the range of the known host plant, Douglas’ silverpuff, includes Baja California; if this gall were to be discovered in Baja California, the silverpuff stem gall wasp would be the only species of herb or bramble gall wasp known from Mexico. 

As mentioned above, this gall is particularly poorly studied, even for herb gall wasps. Some as-of-yet unverified observations suggest that similar galls may occur on other silverpuff species, including other genera such as Uropappus. Whether galls on these hosts prove to be those of the silverpuff stem gall wasp remains uncertain. Galls on Uropappus are addressed at the end of this guide. Thus far, all verifiable observations of this species have occured in April; this must be taken into account if one wants to find these galls. This limited window is likely due to the ephemeral nature of silverpuffs, which have relatively short-lived stems.

Aulacidea nabali
Rattlesnake-root stem gall wasp

Host: Tall rattlesnake-root (Nabalus altissimus). 

Gall location: On the lower stem or roots, often partly or entirely below where the stem meets the soil. 

Description: Typically present as a large, irregular, cylindrical to amorphous cluster of smaller, round, single-chambered galls. Clusters are normally around 1 centimeter in diameter. Internally, the galls are dense and corky, and apparently have the consistency of raw potato. 

Range: This gall has been reported from Ontario and throughout the Northeastern and Midwestern United States, although this species almost certainly occurs throughout more of the host plant’s range.

This gall was originally described from tall rattlesnake-root (Nabalus altissimus), but a subsequent study (Bonnie, 2010) examining organisms associated with nodding rattlesnake-root (N. crepideneus) located galls on that species as well. Lewis H. Weld also reported this gall from white rattlesnake-root (N. albus). It is unknown whether galls on the three host plants are induced by the same species, as this gall has rarely been seen in the recent past and has yet to be closely studied by this guide’s authors.

Antistrophus sp.
Desert-chicory stem gall wasp

Host: Tuberous desert-chicory (Pyrrhopappus grandiflorus). 

Gall location: On the stem, apparently often in the top half. Multiple gall clusters may be found along the same stem. 

Description: These galls are somewhat variable, but they typically appear as clusters of single-chambered, rounded galls around 0.5 centimeters in diameter. Green and fleshy when fresh to rough and brown when dried and old. Sometimes solitary rather than clustered. 

Range: This species has been reported only from Oklahoma and Texas. 

The host plant is also known from Kansas and Nebraska; further sampling may locate this gall in these states. This gall is induced by an undescribed species that may prove to constitute an entirely-new genus of herb gall wasp. Little is known about this species, as it was first found in the late 2010s and was first identified as an undescribed species in 2022.

Aulacidea acroptilonica
Russian knapweed stem gall wasp

Host: Russian knapweed (Rhaponticum repens). 

Gall location: On the stems and branches, often with many galls on the same plant. They seem to most commonly form along leaf nodes. 

Description: Irregular swellings, typically 1-3 centimeter in length. Sometimes short and oval-shaped to greatly elongate and spindle-shaped. Occasionally solitary but more often clustered, often with multiple galls or clusters in rows along the entire length of a stem and its branches. Green and fleshy when fresh to brown and rough when old. 

Range: The exact range of this species in North America is unknown, but it has thus far been found in several Western and Northwestern states (see below). 

The Russian knapweed stem gall wasp was introduced to North America as part of a biological control effort for its host plant, which is considered noxious and a highly-detrimental weed with regard to its impacts on native ecosystems. The extent of this wasp’s release and its current distribution are largely unknown, but it has thus far been encountered in Colorado, Montana, Washington, and Wyoming. Additional populations of Russian knapweed will likely be found to host galls of this species. Biological control documents indicate that at least eight states have established populations, but additional information is unknown at this time.

Antistrophus laciniatus species group
Rosinweed flower gall wasps

Hosts: White rosinweed (Silphium albiflorum), slender rosinweed (S. gracile), prairie rosinweed (S. integrifolium), compass plant (S. laciniatum), cup plant (S. perfoliatum), and prairie dock (S. terebinthinaceum). Galls will probably be discovered on additional rosinweed species as well. 

Gall location: In the disk flowers, often concealed by the outer parts of the flower. 

Description: Oval-shaped, kernel-like, single-chambered galls, typically clustered at the base of the disk flowers. Galls are often hidden, but carefully teasing away the outer flower layers will reveal the galls at the center. In some host plants, the flower is disfigured by the presence of galls (see photo below). 

Range: This species group has been found throughout the Midwestern, Eastern, and South Central United States. Like many other herb galls, this group probably occurs throughout the entire ranges of each species’ respective host.

Historically, it was believed that all flower galls found on rosinweeds were induced by a single species, Antistrophus laciniatus; this species was described by Clarence Gillette in 1891. However, molecular evidence, along with careful morphological observations, suggests that there are several distinct flower gall wasp species on rosinweeds, each of which uses only a subset of the host plants from which flower galls are known. The identities of several of these putative species are still being examined; for instance, it is still unclear whether flower gall wasps on prairie rosinweed (Silphium integrifolium) and cup plant (S. perfoliatum) are induced by one species of gall wasp, or two separate species, each restricted to one host plant. 

An additional species, Antistrophus bicolor, may be a rosinweed flower gall wasp, as it closely resembles other species in this complex. However, this species is known only from a single female collected in the late 1800s, and its host plant is not known. Hopefully, further collecting and rearing of disc flower galls on rosinweed will allow a verifiable association of this species and its true host plant.

Antistrophus sp.

Hosts: slender rosinweed (S. gracile)

Gall location: In the disk flowers, often concealed by the outer parts of the flower. 

Description: Oval-shaped, kernel-like, single-chambered galls, typically clustered at the base of the disk flowers. Galls are often hidden, but carefully teasing away the outer flower layers will reveal the galls at the center. In some host plants, the flower is disfigured by the presence of galls (see photo below). 

Range: This species group has been found throughout the Midwestern, Eastern, and South Central United States. Like many other herb galls, this group probably occurs throughout the entire ranges of each species’ respective host.

Historically, it was believed that all flower galls found on rosinweeds were induced by a single species, Antistrophus laciniatus; this species was described by Clarence Gillette in 1891. However, molecular evidence, along with careful morphological observations, suggests that there are several distinct flower gall wasp species on rosinweeds, each of which uses only a subset of the host plants from which flower galls are known. The identities of several of these putative species are still being examined; for instance, it is still unclear whether flower gall wasps on prairie rosinweed (Silphium integrifolium) and cup plant (S. perfoliatum) are induced by one species of gall wasp, or two separate species, each restricted to one host plant. 

An additional species, Antistrophus bicolor, may be a rosinweed flower gall wasp, as it closely resembles other species in this complex. However, this species is known only from a single female collected in the late 1800s, and its host plant is not known. Hopefully, further collecting and rearing of disc flower galls on rosinweed will allow a verifiable association of this species and its true host plant.

Antistrophus sp.

Hosts: prairie rosinweed (S. integrifolium), cup plant (S. perfoliatum)

Gall location: In the disk flowers, often concealed by the outer parts of the flower. 

Description: Oval-shaped, kernel-like, single-chambered galls, typically clustered at the base of the disk flowers. Galls are often hidden, but carefully teasing away the outer flower layers will reveal the galls at the center. In some host plants, the flower is disfigured by the presence of galls (see photo below). 

Range: This species group has been found throughout the Midwestern, Eastern, and South Central United States. Like many other herb galls, this group probably occurs throughout the entire ranges of each species’ respective host.

Historically, it was believed that all flower galls found on rosinweeds were induced by a single species, Antistrophus laciniatus; this species was described by Clarence Gillette in 1891. However, molecular evidence, along with careful morphological observations, suggests that there are several distinct flower gall wasp species on rosinweeds, each of which uses only a subset of the host plants from which flower galls are known. The identities of several of these putative species are still being examined; for instance, it is still unclear whether flower gall wasps on prairie rosinweed (Silphium integrifolium) and cup plant (S. perfoliatum) are induced by one species of gall wasp, or two separate species, each restricted to one host plant. 

An additional species, Antistrophus bicolor, may be a rosinweed flower gall wasp, as it closely resembles other species in this complex. However, this species is known only from a single female collected in the late 1800s, and its host plant is not known. Hopefully, further collecting and rearing of disc flower galls on rosinweed will allow a verifiable association of this species and its true host plant.

Antistrophus rufus
Rosinweed cryptic stem gall wasp

Hosts: compass plant (S. laciniatum)

Gall location and description: Galls of species in this group are cryptic, meaning they are not outwardly visible and can only be located upon dissection of a galled stem. When dissected, the stem will have numerous brown, oval-shaped chambers along the inside of the pith, each with a single insect. 

Range: This species group has been found throughout the Midwestern, Eastern, and South Central United States. Like many other herb galls, this complex probably occurs throughout the entire ranges of each species’ respective host plant(s). 

As with the rosinweed flower gall wasps, it was once believed that cryptic galls on rosinweeds were all induced by either of two species, Antistrophus minor and A. rufus. Recent data shows that there are multiple species of cryptic stem gall wasps on these plants, each preferring a single host plant. 

Unlike other rosinweeds, compass plant (S. laciniatum) has been found to host two distinct species of cryptic stem gall wasps. These two species are found in the same habitats, and often induce galls on the same individual host plant. The reason for this bizarre occurrence is currently unknown. 

Many unrelated groups of gall wasps seem to have indepdently developed the ability to induce cryptic, inconspicuous galls. The mechanism by which this has been made possible is not known, but it is likely that having hidden galls decreases the odds of attack by predators or parasites. Due to the known diversity of cryptic gall wasps and hidden nature of cryptic galls, it is quite likely that many cryptic galls have thus far evaded detection and await discovery!

Antistrophus minor
Rosinweed cryptic stem gall wasp

Hosts: compass plant (S. laciniatum)

Gall location and description: Galls of species in this group are cryptic, meaning they are not outwardly visible and can only be located upon dissection of a galled stem. When dissected, the stem will have numerous brown, oval-shaped chambers along the inside of the pith, each with a single insect. 

Range: This species group has been found throughout the Midwestern, Eastern, and South Central United States. Like many other herb galls, this complex probably occurs throughout the entire ranges of each species’ respective host plant(s). 

As with the rosinweed flower gall wasps, it was once believed that cryptic galls on rosinweeds were all induced by either of two species, Antistrophus minor and A. rufus. Recent data shows that there are multiple species of cryptic stem gall wasps on these plants, each preferring a single host plant. 

Unlike other rosinweeds, compass plant (S. laciniatum) has been found to host two distinct species of cryptic stem gall wasps. These two species are found in the same habitats, and often induce galls on the same individual host plant. The reason for this bizarre occurrence is currently unknown. 

Many unrelated groups of gall wasps seem to have indepdently developed the ability to induce cryptic, inconspicuous galls. The mechanism by which this has been made possible is not known, but it is likely that having hidden galls decreases the odds of attack by predators or parasites. Due to the known diversity of cryptic gall wasps and hidden nature of cryptic galls, it is quite likely that many cryptic galls have thus far evaded detection and await discovery!

Antistrophus jeanae
Rosinweed cryptic stem gall wasp

Hosts: cup plant (S. perfoliatum)

Gall location and description: Galls of species in this group are cryptic, meaning they are not outwardly visible and can only be located upon dissection of a galled stem. When dissected, the stem will have numerous brown, oval-shaped chambers along the inside of the pith, each with a single insect. 

Range: This species group has been found throughout the Midwestern, Eastern, and South Central United States. Like many other herb galls, this complex probably occurs throughout the entire ranges of each species’ respective host plant(s). 

As with the rosinweed flower gall wasps, it was once believed that cryptic galls on rosinweeds were all induced by either of two species, Antistrophus minor and A. rufus. Recent data shows that there are multiple species of cryptic stem gall wasps on these plants, each preferring a single host plant. 

Unlike other rosinweeds, compass plant (S. laciniatum) has been found to host two distinct species of cryptic stem gall wasps. These two species are found in the same habitats, and often induce galls on the same individual host plant. The reason for this bizarre occurrence is currently unknown. 

Many unrelated groups of gall wasps seem to have indepdently developed the ability to induce cryptic, inconspicuous galls. The mechanism by which this has been made possible is not known, but it is likely that having hidden galls decreases the odds of attack by predators or parasites. Due to the known diversity of cryptic gall wasps and hidden nature of cryptic galls, it is quite likely that many cryptic galls have thus far evaded detection and await discovery!

Antistrophus meganae
Rosinweed cryptic stem gall wasp

Hosts: prairie dock (S. terebinthinaceum)

Gall location and description: Galls of species in this group are cryptic, meaning they are not outwardly visible and can only be located upon dissection of a galled stem. When dissected, the stem will have numerous brown, oval-shaped chambers along the inside of the pith, each with a single insect. 

Range: This species group has been found throughout the Midwestern, Eastern, and South Central United States. Like many other herb galls, this complex probably occurs throughout the entire ranges of each species’ respective host plant(s). 

As with the rosinweed flower gall wasps, it was once believed that cryptic galls on rosinweeds were all induced by either of two species, Antistrophus minor and A. rufus. Recent data shows that there are multiple species of cryptic stem gall wasps on these plants, each preferring a single host plant. 

Unlike other rosinweeds, compass plant (S. laciniatum) has been found to host two distinct species of cryptic stem gall wasps. These two species are found in the same habitats, and often induce galls on the same individual host plant. The reason for this bizarre occurrence is currently unknown. 

Many unrelated groups of gall wasps seem to have indepdently developed the ability to induce cryptic, inconspicuous galls. The mechanism by which this has been made possible is not known, but it is likely that having hidden galls decreases the odds of attack by predators or parasites. Due to the known diversity of cryptic gall wasps and hidden nature of cryptic galls, it is quite likely that many cryptic galls have thus far evaded detection and await discovery!

Antistrophus sp.
Rosinweed cryptic stem gall wasp

Hosts: prairie rosinweed (S. integrifolium)

Gall location and description: Galls of species in this group are cryptic, meaning they are not outwardly visible and can only be located upon dissection of a galled stem. When dissected, the stem will have numerous brown, oval-shaped chambers along the inside of the pith, each with a single insect. 

Range: This species group has been found throughout the Midwestern, Eastern, and South Central United States. Like many other herb galls, this complex probably occurs throughout the entire ranges of each species’ respective host plant(s). 

As with the rosinweed flower gall wasps, it was once believed that cryptic galls on rosinweeds were all induced by either of two species, Antistrophus minor and A. rufus. Recent data shows that there are multiple species of cryptic stem gall wasps on these plants, each preferring a single host plant. 

Unlike other rosinweeds, compass plant (S. laciniatum) has been found to host two distinct species of cryptic stem gall wasps. These two species are found in the same habitats, and often induce galls on the same individual host plant. The reason for this bizarre occurrence is currently unknown. 

Many unrelated groups of gall wasps seem to have indepdently developed the ability to induce cryptic, inconspicuous galls. The mechanism by which this has been made possible is not known, but it is likely that having hidden galls decreases the odds of attack by predators or parasites. Due to the known diversity of cryptic gall wasps and hidden nature of cryptic galls, it is quite likely that many cryptic galls have thus far evaded detection and await discovery!

Antistrophus sp. 
Rosinweed cryptic stem gall wasp

Hosts: toothed rosinweed (S. dentatum)

Gall location and description: Galls of species in this group are cryptic, meaning they are not outwardly visible and can only be located upon dissection of a galled stem. When dissected, the stem will have numerous brown, oval-shaped chambers along the inside of the pith, each with a single insect. 

Range: This species group has been found throughout the Midwestern, Eastern, and South Central United States. Like many other herb galls, this complex probably occurs throughout the entire ranges of each species’ respective host plant(s). 

As with the rosinweed flower gall wasps, it was once believed that cryptic galls on rosinweeds were all induced by either of two species, Antistrophus minor and A. rufus. Recent data shows that there are multiple species of cryptic stem gall wasps on these plants, each preferring a single host plant. 

Unlike other rosinweeds, compass plant (S. laciniatum) has been found to host two distinct species of cryptic stem gall wasps. These two species are found in the same habitats, and often induce galls on the same individual host plant. The reason for this bizarre occurrence is currently unknown. 

Many unrelated groups of gall wasps seem to have indepdently developed the ability to induce cryptic, inconspicuous galls. The mechanism by which this has been made possible is not known, but it is likely that having hidden galls decreases the odds of attack by predators or parasites. Due to the known diversity of cryptic gall wasps and hidden nature of cryptic galls, it is quite likely that many cryptic galls have thus far evaded detection and await discovery!

Antistrophus sp. 
Rosinweed cryptic stem gall wasp

Hosts: Whorled rosinweed (S. asteriscus var. trifoliatum)

Gall location and description: Galls of species in this group are cryptic, meaning they are not outwardly visible and can only be located upon dissection of a galled stem. When dissected, the stem will have numerous brown, oval-shaped chambers along the inside of the pith, each with a single insect. 

Range: This species group has been found throughout the Midwestern, Eastern, and South Central United States. Like many other herb galls, this complex probably occurs throughout the entire ranges of each species’ respective host plant(s). 

As with the rosinweed flower gall wasps, it was once believed that cryptic galls on rosinweeds were all induced by either of two species, Antistrophus minor and A. rufus. Recent data shows that there are multiple species of cryptic stem gall wasps on these plants, each preferring a single host plant. 

Unlike other rosinweeds, compass plant (S. laciniatum) has been found to host two distinct species of cryptic stem gall wasps. These two species are found in the same habitats, and often induce galls on the same individual host plant. The reason for this bizarre occurrence is currently unknown. 

Many unrelated groups of gall wasps seem to have indepdently developed the ability to induce cryptic, inconspicuous galls. The mechanism by which this has been made possible is not known, but it is likely that having hidden galls decreases the odds of attack by predators or parasites. Due to the known diversity of cryptic gall wasps and hidden nature of cryptic galls, it is quite likely that many cryptic galls have thus far evaded detection and await discovery!

Antistrophus silphii species group
Rosinweed terminal stem gall wasps 

Hosts: Whorled rosinweed (S. asteriscus var. trifoliatum), prairie rosinweed (S. integrifolium), and cup plant (S. perfoliatum). 

Gall location: On the stem, almost always at the apex. 

Description: Many-chambered, oval-shaped to spherical galls, 1-5 centimeters in length and usually of similar diameter. Often adorned with aborted leaves, and only rarely with the stem continuing beyond the end of the gall. Green and fleshy when fresh to brown and rough when dry. Both fresh and dry galls are rather hard and corky. 

Range: This species group has been found throughout the Midwestern and Eastern United States. Each of the three hosts overlap over much of their range. They are apparently most common in the Midwest. 

Terminal stem galls on prairie rosinweed and cup plant have long been considered the same species, A. silphii. However, it has long been suspected that galls on either host plant are induced by separate but closely-related species; the active periods of wasps on either host do not largely overlap, and gall size seems to vary between the two host. Terminal stem galls on whorled rosinweed were just discovered for the first time within the last year. Further research will unveil the true identities of gall wasps across the three host plants.

Antistrophus silphii species group
Rosinweed terminal stem gall wasps

Hosts: Whorled rosinweed (S. asteriscus var. trifoliatum), prairie rosinweed (S. integrifolium), and cup plant (S. perfoliatum).

Gall location: On the stem, almost always at the apex.

Description: Many-chambered, oval-shaped to spherical galls, 1-5 centimeters in length and usually of similar diameter. Often adorned with aborted leaves, and only rarely with the stem continuing beyond the end of the gall. Green and fleshy when fresh to brown and rough when dry. Both fresh and dry galls are rather hard and corky.

Range: This species group has been found throughout the Midwestern and Eastern United States. Each of the three hosts overlap over much of their range. They are apparently most common in the Midwest.

Terminal stem galls on prairie rosinweed and cup plant have long been considered the same species, A. silphii. However, it has long been suspected that galls on either host plant are induced by separate but closely-related species; the active periods of wasps on either host do not largely overlap, and gall size seems to vary between the two host. Terminal stem galls on whorled rosinweed were just discovered for the first time within the last year. Further research will unveil the true identities of gall wasps across the three host plants.

Antistrophus spp.
Rosinweed cryptic leaf gall wasps

Hosts: Compass plant (S. laciniatum) and prairie dock (S. terebinthinaceum)

Gall location and description: Species belonging to this group induce galls in the petioles and occasionally larger veins of the leaves. Thus far, galls seem to only be induced in the basal leaves, but it is possible that galls are also induced in leaves on the main stem. As with several other herb gall wasps, galls of species in this group are cryptic and leave no discernable trace on the surface of the leaf. When dissected, the leaf will reveal numerous brown, oval-shaped chambers along the inside of the pith, each with a single insect.

Range: Galls of this species group have only been found in Iowa, Ohio, and Wisconsin thus far, but they can probably be found throughout the native ranges of the host plants.

The rosinweed cryptic leaf gall wasps appear to be related to those inducing cryptic galls in rosinweed stems, but their exact relation is unknown. Whether galls on the two hosts comprise one or two species also remains to be seen. These galls were just recently discovered, and more research is necessary to understand their biology and locate possible additional host plants.

Phanacis taraxaci
Dandelion gall wasp

Host: Dandelion (Taraxacum officinale).

Gall location: On the leaf, often extending from the very base of the leaf all the way up the petiole and midrib.

Description: Spherical to oval-shaped, blister-like, single-chambered galls, often only a few millimeters in length. Typically quite abundant, and sometimes with multiple adjacent galls clustered together or otherwise confluent.

Range: Dandelions are found throughout North America, but thus far, this gall has only been observed in a handful of northern states and provinces, including Pennsylvania, Michigan, Minnesota, Oregon, Quebec, and Saskatchewan. These galls certainly exist elsewhere within the range of the host plant.

This species was introduced to North America from Europe along with its host plant. Interestingly, this gall was first described in North America prior to its discovery in Europe. Because dandelions are often considered weeds and are frequently culled, this gall generally appears to be more common in areas that are not actively maintained.

The dandelion gall wasp and the catsear gall wasp (Phanacis hypochoeridis), both of which are introduced species, are the only representatives of the gall wasp tribe Phanacidini to be found in North America.

Liposthenes glechomae
Ground-ivy gall wasp

Host: Ground-ivy (Glechoma hederacea). 

Gall location: Somewhat variable, usually on the leaf or petiole, but occasionally appearing on the stem. 

Description: Single-chambered, spherical to amorphous galls. Usually solitary, but occasionally may appear clustered or confluent. Usually with short, pale hairs across the surface. Small and reddish when fresh to larger and greener when more mature. Old, dry galls appear brown and papery. 

Range: Currently, this species has been found in Northeastern North America including many U.S. states and adjacent areas of Canada. Ground-ivy has been widely introduced and it is possible that this species will be discovered elsewhere. 

This species was introduced to North America from Europe, where it is widespread and quite common. No native gall wasps are known in association with the mint family. 

It has also had a tumultuous taxonomic history, and has previously been classified in many, many gall wasp genera over the centuries since its discovery by Linnaeus in 1758. 

Interestingly, this species is comprised entirely of parthenogenetic females, meaning all reproduction is asexual and without the involvement of males. Parthenogenesis is known in a couple other herb gall wasps, but this type of reproduction is not unheard of in the order Hymenoptera.

Diastrophus fragariae
Strawberry leaf petiole gall wasp

Host: Virginia strawberry (Fragaria virginiana). 

Gall location: On the leaf petiole. 

Description: Multiple-chambered swellings, usually cylindrical. Often with a segmented appearance due to the positioning of chambers in a distinct row within the gall tissue. Sometimes with fine hairs. 2-6 centimeters in length and less than a centimeter in diameter. Green to red when fresh to brown when dried and old. 

Range: This gall likely occurs throughout the range of the Virginia strawberry, but thus far is known from the Northeast and Upper Midwest, and is especially well-sighted in New England. 

This gall has been found in both natural and cultivated systems. Mature galls may be difficult to locate in the field as the stems and leaves of the host plant are prone to withering. However, plants bearing fresh galls may be transplanted and cared for so as to allow the gall to mature.

Diastrophus fusiformans
Cinquefoil petiole spindle gall wasp

Host: Slender cinquefoil (Potentilla gracilis). 

Gall location: On the leaf petiole, although some accounts state that this gall forms on the stem. 

Description: Multiple-chambered swellings ranging from 3-10 centimeters in length. Usually spindle-shaped, but often greatly curved or otherwise deformed. Sometimes with fine hairs. Pithy internally, with chambers suspended in the internal pith. Green to red when fresh to brown when dried and old. Similar to the cinquefoil stem spindle gall wasp (see page 39). 

Range: Thus far known from Oregon and Washington, but likely far more widespread throughout the range of slender cinquefoil, at least in Western North America. 

This gall, like many others, is realtively poorly known. Interestingly, the slender cinquefoil is quite common and widespread, but this gall is only rarely seen.

Diastrophus niger
Cinquefoil stem spindle gall wasp 

Host: Dwarf cinquefoil (Potentilla canadensis). 

Gall location: Usually on the stem, but occasionally extending onto the petiole. 

Description: Similar in size and appearance to the cinquefoil petiole spindle gall wasp. Spindle-shaped, multiple-chambered swellings. Unlike the cinquefoil petiole spindle gall, the stem spindle gall is not usually curved. The two galls occur on different cinquefoil species, and the identity of the host plant is often necessary to distinguish between the two. 

Range: This gall has most often been encountered in the Northeastern United States from Connecticut to south New Jersey, and almost certainly occurs in adjacent parts of Canada. Museum records indicate that this gall may be found as far south as Arkansas, but this requires further substantiation. 

This gall wasp was originally described as two separate species, the other being Diastrophus minimus. They have since been synonymized, but previous work on cinquefoil gall wasps has been largely incomplete, and further research may call this synonymy into question. This gall has also been reported in association with tall cinquefoil (Drymocallis arguta), but such records likely represent a separate, undescribed species (see “unverified galls and hosts”).

Diastrophus potentillae
Cinquefoil bud gall wasp

Host: Dwarf cinquefoil (Potentilla canadensis) and common cinquefoil (P. simplex). 

Gall location: On the axil. Description: Single-chambered, globular swellings 8-13 millimeters in diameter. Sometimes with fine hairs. The chamber resides at the center of the gall and is surrounded by fleshy material that becomes spongy as the gall matures. Often with leaf remnants growing out of the outermost layer. Green when fresh to reddish in later stages. 

Range: Throughout Northeastern and North-central North Ameica, from Nova Scotia west to Minnesota and south to North Carolina and Tennessee. 

This gall is often quite locally abundant, as its two host plants are rather weedy and occur in high density, especially in nutrient-poor environments.

Diastrophus tumefactus
Rough cinquefoil gall wasp

Host: Norwegian cinquefoil (Potentilla norvegica var. monspeliensis). 

Gall location: On the stem. 

Description: Nodular swellings that are multiple-chambered or agglomerate, with many cells in close vicinity. Up to 3 centimeters in length and 2 centimeters in diameter. When several galls are confluent, they may form clusters up to 7 centimeters in length. Shape is apparently quite variable, from subspherical to entirely amorphous. Generally smooth or bark-like and with minute, blunt spines. 

Range: Thus far, this gall has only been reported from Ontario and Quebec. 

This gall is poorly known. It was described by Alfred C. Kinsey from adults dissected from galls collected 40 years prior, and the gall has been rarely reported since. The gall was described from only the Norwegian cinquefoil variety monspeliensis, but it is unknown of they occur on other varieties.

Diastrophus bassettii
Dewberry crown gall wasp 

Host: Common dewberry (Rubus flagellaris) and swamp dewberry (R. hispidus). 

Gall location: On the crown, at the interface of the stem and root, either above or below the soil line. In rare occasions, this gall can be found further up on the stem and may be mistaken for the similar galls, especially if the host plant is not identified to species. 

Description: Multiple-chambered, globular swelling. Sometimes nearly spherical, but usually appearing as an amorphous botryoidal cluster of kernel-like chambers. Greenish to reddish when fresh. Highly variable in size, usually 1-3 centimeters in diameter but occasionally larger. 

Range: Historically, this gall has been found throughout the Northeastern United States, but some records suggest it occurs as far south as North Carolina. 

This gall was rather poorly known until the recent past. They are often locally abundant, and can often be found by locating a single gall and following the stems to find additional galls, even on the same plant.

Diastrophus cuscutaeformis
Blackberry seed gall wasp

Host: Various brambles (see remarks below). 

Gall location: On the main stem. 

Description: Distinctive, but often quite diverse in appearance. Typically present as large, long clusters of closely-placed, seed-like, single-chambered galls. Green when fresh to red or brown when mature. The size and shape of the individual galls is quite variable, although they usually each have fine hairy filaments, distinct spines, or blunt projections. Individual galls are less than a half centimeter in diameter. Clusters may contain only a few galls, or as many as 100! 

Range: Widespread in Eastern North America, from New England and Lower Canada south to Georgia and west to Minnesota and Louisiana. This gall is one of the more common bramble galls, and it is common in many habitat types. 

There is currently little consnsus on the true host plant range for this species, as the literature has been inconsistent in its mentioning and treatment of host identifications, but overall, this gall appears to be found on brambles of the subgenus Rubus, specifically species that stand erect. The authors of this guide have thus far found blackberry seed galls on Allegheny blackberry (Rubus allegheniensis) and common blackberry (R. canadensis). Host plants used by this gall can be difficult to identify, but luckily, this gall is rather distinctive.

Diastrophus kincaidii
Thimbleberry gall wasp

Host: Thimbleberry (Rubus parviflorus). 

Gall location: On the stem. 

Description: Large, irregular, multiple-chambered swellings, up to 6 centimeters in length and 2 centimeters in diameter. Sometimes rounded but often club-shaped, spindle-shaped, vaguely gnarled and twisted, or otherwise deformed. Generally smooth and covered with spots of rough, bark-like tissue. Greenish to reddish and fleshy when fresh to brown when old and dry. 

Range: This gall occurs in two distinct, isolated populations: one in Western North America from northern British Columbia south to most of California and east to Montana, and another in the Great Lakes region in Ontario, Minnesota, Wisconsin, and Michigan. It has been theorized that the two distinct populations are the result of glaciation. 

A second species, currently known as Diastrophus austrior, has often been split off from this species based on specimens collected in California. The status of this second species is uncertain but will hopefully be resolved in the near future. Galls on this host plant are especially easy to distinguish, as thimbleberry has no thorns.

Diastrophus nebulosus
Blackberry knot gall wasp

Host: Various brambles (see remarks below). 

Gall location: On the main stem. 

Description: Large, multiple-chambered swellings, up to 8 centimeters in length and up to 3 centimeters in diameter. Often botryoidal, appearing as a globular, amorphous swelling, but extremely variable overall. Usually with distinct longitudinal grooves running parallel to the stem, but plants growing in poorer soil are apparently smoother and lack grooves. Smaller galls with fewer chambers often appear more nodular. Also quite variable in color, greenish to reddish when fresh and reddish to brown when old. 

Range: Widespread in the Eastern United States, from New England west to Minnesota and south to Georgia and Texas. Similar to the blackberry seed gall wasp, host records for this species are not well established. Thus far, verifiable host records for this gall include several species belonging to the bramble subgenus Rubus: Allegheny blackberry (Rubus allegheniensis), sand blackberry (R. cuneifolius), and the hybrid species boysenberry (R. ursinus x idaeus). As with the blackberry seed gall, host plants used by this gall can be difficult to identify, but the distinctive nature of this gall often makes it identifiable in the absence of a proper host identification.

Diastrophus radicum
Irregular bramble root gall wasp 

Host: Northern dewberry (Rubus flagellaris) and black raspberry (R. occidentalis). 

Gall location: On the roots, always below the surface of the soil. 

Description: A many-chambered swelling. Highly variable in shape and size, ranging from pea-shaped and less than a half centimeter to amorphous and globular, three centimeters in diameter. 

Range: Fairly widespread, from New England south to North Carolina. Some less-verifiable records indicate that this gall occurs as far south and west as Louisiana. 

The two host species on which this gall is found belong to two different subgenera, making the irregular bramble root gall rather unique amongst bramble galls. It is possible that galls on either host are actually separate species, but this has yet to be substantiated.

Diastrophus turgidus
Red raspberry knot gall wasp

Host: Red raspberry (Rubus strigosus). 

Gall location: On the stem. 

Description: Large, multiple-chambered swellings rather similar in appearance to the blackberry knot gall. Generally smooth and fleshy, but usually densely covered with thorns. Unlike the blackberry knot gall, the red raspberry knot gall lacks distinct longitudinal grooves and is instead rather regular in its surface texture. Reddish to greenish and fleshy when fresh to brown and dry when old. 

Range: Likely widespread, thus far known along the border of the US and Canada as well as Alaska and some records from Central Canada. 

This gall is rather poorly known, as demonstrated by its disparate range. The range and appearance of this gall separate it from the blackberry knot gall.

Aulacidea ambrosiaecola
Ragweed stem gall wasp 

Host: Ragweed (Ambrosia sp.).

Gall location: On the stem.

Range: Missouri.

This species was described from adult wasps apparently reared from a gall on the stem of a ragweed plant. Nothing is known of the gall, as William Ashmead, who described this species, was sent only a handful of wasps by a friend, who only provided meager notes on their supposed biology, including a possible association with a moth. Nothing further is known of this species, and it has not been encountered since with the exception of a few unverifiable specimens from museum collections. If these museum records are considered correct, the ragweed stem gall wasp may induce cryptic galls rather than outwardly-perceptible galls.

Presumed Diastrophus sp.
Wood beauty stem gall wasp 

Host: Wood beauty (Drymocallis sp.).

Gall location: On the stem

Description: Globular galls similar to those of the cinquefoil stem spindle gall wasp (see page 39); galls of this species are often misidentified as that species. Range: Widespread, probably throughout the range of wood beauty in North America. 

Galls have been reported on three wood beauty species (Drymocallis arguta, D. glandulosa, and D. lactea). The true inducer of these galls is entirely unknown but is presumed to be a gall wasp

Presumed Diastrophus sp.

Host: Sierra horkelia (Horkelia congesta congesta).

Gall location: On the stems.

Range: Thus far reported from Oregon.

An unknown stem gall has been recorded on a subspecies of Sierra horkelia that is endemic to the Willamette and Umpqua Valleys in Oregon. The true inducer of this gall is unknown, but dissections of several galls have yielded what appear to be gall wasp larvae. Further research will determine the identity of this gall in the near future.

Southern dewberry stem gall

Host: Southern dewberry (Rubus trivialis).

Gall location: On the stem.

Description: Irregular stem swellings.

Range: Mississippi.

Not much is known about this gall, as it is known only from a single specimen. It may be induced by a midge rather than a gall wasp, but the inducer is not yet known

Mossy bramble gall

Host: Bramble (Rubus sp.).

Gall location: On the leaf.

Description: Small to medium-sized swellings covered in fine, mossy, hairlike projections. Similar in appearance to the mossy rose gall (Diplolepis rosae) which occurs on roses (Rosa arvensis and R. canina). 

Range: Thus far reported in Ohio and Pennsylvania. 

As with the southern dewberry stem gall, virtually nothing is known of this gall. The inducer is entirely unknown, and there is a chance that the true inducer of this gall is a midge rather than a gall wasp.

Presumed Antistrophus sp.
Silverpuff basal stem gall wasp

Host: Lindley’s silverpuff (Uropappus lindleyi).

Gall location: At the base of the stem.

Description: A spherical swelling, often with dense felt-like pubescence. Greenish to reddish, and apparently around 1-2 centimeters in diameter.

Range: California.

The silverpuff stem gall wasp (see page 23) induces galls on a closely-related host plant, but the silverpuff basal stem gall wasp appears rather distinct, particularly in its location on the host plant and the outer pubescence. The inducer of this gall is unknown, but it is probably a gall wasp closely related to the silverpuff stem gall wasp.

Host: Prairie rosinweed (S. integrifolium) and cup
plant (S. perfoliatum).

Gall location: On the stem, at least several centimeters from the apex, and often in the lower
half. Multiple gall clusters may be found alongthe same stem.

Description: These galls are somewhat variable, but they often appear as clusters of single-chambered, rounded galls around less than 1 centimeter in diameter. Occasionally, the clustered galls are so densely packed that they appear as one large, amorphous gall. Green and fleshy and often with brown, dry areas when fresh, to entirely rough and brown when dried and old.

Range: Thus far, these galls have only beenfound in Iowa, Kansas, Missouri, and Ohio. However, they were only recently seen for the first time, and likely occur elsewhere within the native ranges of the two host plants.

Field Guide to the Herb and Bramble Gall Wasps of North America