The gall's range is computed from the range of all hosts that the gall occurs on. In some cases we have evidence that the gall does not occur across the full range of the hosts and we will remove these places from the range. For undescribed species we will show the expected range based on hosts plus where the galls have been observed.
Gall. (Plate XXVII, Figs. 4, 5). On the roots of running blackberry or dewberry (Rubus canadensis), and probably allied species. Polythalamous. Brown, pithy and irregular in shape, varying in size from the shape of a pea of two inches or more in length and nearly an inch in diameter. Sometimes the entire root stalk above and below the surface of the ground, is surrounded by almost a solid mass of galls, measuring about three inches in diameter.
Habitat: Canada to North Carolina; Michigan, Colorado.
The fly is allied to D. turgidus, but may be readily separated by the absence of the brown color of the radial vein before reaching the second cross-vein. I have taken galls on the roots of the black raspberry or blackcaps (Rubus occidentalis) which may prove to be the same as D. radicum. According to Bassett the galls also may be found on the roots of the high bush blackberry (Rubus villosus). The types are in the American Museum of Natural History and American Entomological Society.
