Biology
Antistrophus rufus induces inconspicuous, externally imperceptible galls in stems of Silphium laciniatum (Fig. 8H) (Tooker et al. 2004; Nastasi and Deans 2021). Records associating A. rufus with other host plants most likely represent distinct species including the other species addressed in the present work.

Distribution
Antistrophus rufus was described from material collected in Illinois (USA) and has since been reported from Kansas (Tooker et al. 2004; Nastasi and Deans 2021). Additional material that we examined revealed additional records from Iowa and Wisconsin, and reiterated occurrence of this species in Kansas (Suppl. material 1: table 1). Known and potential distribution are summarized in Fig. 9.

Remarks
Kieffer (1902) synonymized Antistrophus with Aylax (=Aulax) Hartig, 1840. Some authors (e.g., Beutenmüller 1910) follow Kieffer’s synonymy, but others appear to have rejected or otherwise omitted this change from many works treating the group (e.g., Weld 1951; Nieves-Aldrey 1994). This generic synonymy and the resulting species synonyms were accidentally omitted from Nastasi and Deans’ (2021) catalogue, and we are unable to locate a nomenclatural act reinstating Antistrophus as a valid genus. The genus Aylax has now long been regarded to include only two species of gall wasps inducing galls on Papaver (Papaveraceae) (Nieves-Aldrey 1994; Ronquist et al. 2015). Additionally, the two genera are now placed in different tribes: Aylax is now placed in the tribe Aylacini, while Antistrophus is placed in the Aulacideini. We regard here Antistrophus as a valid genus independent of Aylax, although Antistrophus represents a heterogeneous assemblage as currently defined based on preliminary data from an ongoing revisionary study (Nastasi et al., unpublished data).

- Louis F. Nastasi, John F. Tooker, Charles K. Davis, Cecil N. Smith, Timothy S. Frey, M. J. Hatfield, Tara M. Presnall, Heather M. Hines, Andrew R. Deans: (2024) Cryptic or underworked? Taxonomic revision of the Antistrophus rufus species complex (Cynipoidea, Aulacideini)^©