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Genus Antistrophus

Cynipidae, Antistrophus laciniatus - Antistrophus laciniatus Cynipidae, wasp (red) - Antistrophus lygodesmiaepisum Rosinweed Stem Gall - Antistrophus silphii Cynipidae on Compass Plant, #2 gall opened - Antistrophus laciniatus - female Cynipidae on Compass Plant, #3 gall opened - Antistrophus laciniatus Silphium stem wasp, ventral - Antistrophus Rosinweed Stem Gall, the male, lateral - Antistrophus silphii - male Cynipidae galls on Compass Plant - Antistrophus laciniatus
Classification
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Hymenoptera (Ants, Bees, Wasps and Sawflies)
No Taxon ("Parasitica" - Parasitoid Wasps)
Superfamily Cynipoidea
Family Cynipidae (Gall Wasps)
Tribe Aulacideini (Herb Gall Wasps)
Genus Antistrophus
Other Common Names
Rosinweed gall wasps (for seven species)
Pronunciation
an-TIS-troh-fuhs
Synonyms and other taxonomic changes
Antistrophus Walsh, 1869
Asclephiadiphila Ashmead, 1897
Numbers
10 described species, all known from America north of Mexico:
Antistrophus bicolor Gillette, 1897 (known only from a single female collected in Illinois)
Antistrophus chrysothamni (Beutenm├╝ller, 1908) (induces polythalmous galls in stems of Chrysothamnus; reported only from Arizona)
Antistrophus jeanae Tooker & Hanks, 2004 (induces cryptic galls in stems of Silphium terebinthinaceum; widespread)
Antistrophus laciniatus Gillette, 1897 (induces ovoid galls in disc flowers of Silphium laciniatum; widespread)
Antistrophus lygodesmiaepisum Walsh, 1869 (induces monothalmous globular galls on stems of Lygodesmia juncea; widespread)
Antistrophus meganae Tooker & Hanks, 2004 (induces cryptic galls in stems of Silphium perfoliatum; widespread)
Antistrophus microseris (McCracken & Egbert, 1922) (induces polythalmous galls in stems of Microseris; reported only from California)
Antistrophus minor Gillette, 1897 (induces cryptic galls in stems of Silphium laciniatum; widespread)
Antistrophus rufus Gillette, 1897 (induces cryptic galls in stems of Silphium laciniatum; widespread)
Antistrophus silphii Gillette, 1897 (induces large globular galls on terminal stems of Silphium integrifolium; widespread)

Many, many undescribed species exist, particularly in association with Silphium host plants. Several undescribed species are currently lumped with described taxa (e.g., galls of "Antistrophus silphii" on Silphium perfoliatum stems or galls of "Antistrophus laciniatus" in flowers of other Silphium species).
Size
Approximately 1-5 mm in length, with size varying greatly depending on the species.
Identification
Among other North American herb gall wasps of tribe Aulacideini, Antistrophus can be recognized by the combination of the sculpturing of the mesopleuron (striate to reticulate) and the open radial cell of the fore wing. Further taxonomic work on this genus will refine the diagnostic characters. Most Antistrophus species are cryptic and cannot easily be distinguished from closely-related species on the basis of morphology alone. Host plant identification as well as images of galls will greatly increase the probability of identification.
Range
Throughout North America. Ranges for each species are greatly dependent on distribution of possible host plants.
Habitat
Most abundant in tallgrass prairies but found wherever host plants occur.
Season
Adults are active in spring/summer. Larvae overwinter in galls in host tissue.
Food
Galls are induced on Chrysothamnus, Lygodesmia, Microseris, and Silphium (1).
Life Cycle
Galls are induced by adult female wasps during the spring/summer for a one- or two-week period (dependent on the species). Offspring overwinter in host tissue and emerge the following spring/summer. Galled plant tissue should be collected for rearing only after host plants have senesced.
Galls of multiple Antistrophus may be found in on the same individual plants in the same host organ. For instance, it is quite common for stems of compass plant (Silphium laciniatum) to rear both Antistrophus minor and rufus.
Remarks
This genus is likely polyphyletic on the basis of morphology and biology. Antistrophus chrysothamni and microseris were transfered from Aylax by Weld without explanation; new genera will likely be described for these two species.
Antistrophus lygodesmiapisum has been shown to induce multiple distinct types of galls on Lygodesmia juncea, but these galls will likely turn out to be independent species erroneously recognized as conspecific.
See Also
In North America, galls on herbaceous plants are also induced by Aulacidea, Diastrophus, Liposthenes, and Phanacis (1).