#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.

#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.

#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.

#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.

#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.

Posted on August 29, 2023 07:47 PM by louisnastasi