This species has two generations per year, both of which develop in rhizome galls. The spring generation galls are solitary or clustered, bulbous, fleshy masses with 1β8 chambers each. As the galls develop, they become apparent above the ground and burst open before adult emergence in early May ... The second generation galls constitute brownish, globular, and usually multi-chambered swellings of the rhizomes, which were still completely subterranean in mid August, when they contained mature larvae. Pupation took place in late August to early September, at which time the galls became elongate and fleshier. Shortly before adult emergence the galls became apparent above the soil surface, and adults emerged from mid to late September.
β- 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 AmericaΒ©