Felt (1908) described this species from a single male and a single female and speculated (Felt 1915) that it develops as an inquiline in galls of R. capitata. However, we did not find any signs of its presence in galls of R. capitata. Given the morphological similarity of R. inquisitor adults to those of R. clarkei, it is possible that R. inquisitor is not an inquiline but, rather, induces inconspicuous conical galls that escaped Felt’s attention. In the present study we found such galls on leaves of S. gigantea ... including on modified leaves composing the bud galls of Dasineura folliculi. This finding supports our hypothesis that R. inquisitor may well be the species responsible for these galls, but the galls were rare and we were unable to rear adults from them ... A comparison of such adults with the type specimens of R. inquisitor would be the only way to determine whether the galls we found are indeed those of R. inquisitor. ...
Galls of this species [given as Rhopalomyia sp. ] are very similar in shape and size to galls of R. clarkei on S. rugosa, but are much rarer and are smooth rather than hairy. They are 2–3.3 mm long and 0.5–0.7 wide at widest part, green, sometimes with dark longitudinal lines, and most were found on the upper side of leaves. Due to the scarcity of the galls and to high parasitism rates we were unable to rear adults from them, but a molecular analysis based on larvae indicated that this species differs from R. clarkei (Dorchin et al., in prep.). Some galls were found on leaves composing the bud galls of Dasineura folliculi on S. gigantea and there is no reason to believe they do not occur also on modified leaves of the rosette gall induced by R. capitata on the same host plant. If this is indeed the case, then these galls may actually be those of R. inquisitor, which was reported by Felt (1908) as an inquiline in R. capitata galls (see details under R. inquisitor).

- Netta Dorchin, Miles V. McEvoy, Todd A. Dowling, Warren G. Abrahamson, Joseph G. Moore: (2009) Revision of the goldenrod-galling Rhopalomyia species (Diptera: Cecidomyiidae) in North America^©