Diplolepis variabilis (Bassett)

Diplolepis variabilis was first described from galls collected in North Dakota (Bassett 1890). Beutenmüller (1907) and Kinsey (1922) reported galls from Washington to Texas. In Canada, D. variabilis is found only west of the Rocky Mountains and is very common on tall R. woodsii from Kelowna to Osoyoos, British Columbia. Galls of D. variabilis are found on the leaves of the upper branches and are usually larger and denser than galls of D. ignota.

Galls are single-chambered and spherical and are found on the abaxial surface of leaflets. However, most galls coalesce to make clusters irregularly rounded and globular to ovate (Fig. 30). Single-chambered galls are about 8 mm in diameter, whereas coalesced galls are often 2 cm in diameter. They have a smooth surface and internally are pith-like with the consistency of packed sawdust. The chambers are located at the centre, deep within the galls (Fig. 31). Galls are green when immature but turn tan to brown when mature. They are often so dense that branches droop with the combined weight of the galls. They remain on the host plants over winter. Galls are initiated in late summer.

Inhabitants were reared from a large population of galls collected in the fall near Oliver, British Columbia. Of recovered insects (Fig. 44K), 7.7% were inducers, 23.2% were Periclistus, and 69.3% were parasitoids. The most abundant parasitoids were Aprostocetus at 47.5% and Eurytoma at 17%.

- Joseph Shorthouse, KD Floate: (2010) Galls induced by cynipid wasps of the genus Diplolepis (Hymenoptera: Cynipidae) on the roses of Canada's grasslands^©