Diplolepis gracilis (Ashmead)

Diplolepis gracilis was first described from galls collected at an undisclosed site in the northeastern United States (Ashmead 1897). Little is known about the distribution of D. gracilis. However, it has been recorded from several northern states (Thompson 1915; Olson 1964; Burks 1979). On the prairies, galls are found on roses growing in shaded areas along the North Saskatchewan River in Edmonton, Alberta, eastward toward Prince Albert, Saskatchewan, and northward along the South Saskatchewan River from the Alberta– Saskatchewan border.

Mature galls are ellipsoid, averaging 4–6 mm in diameter, have blunt protuberances extending from the lateral circumference, and are on the abaxial surface of leaflets (Fig. 26). They are single-chambered (Fig. 27) with thin walls. Maturing galls are white and although they are usually found in rows, adjacent galls seldom coalesce. Mature galls turn light tan and fall with their host leaves in mid-September. Galls are initiated in late summer.

A large population of galls found near Douglas Provincial Park in Saskatchewan illustrates a typical community for this species (Fig. 44H), of which 12.7% were inducers and 21% were Periclistus. The most abundant parasitoids were Orthopelma (at 30.5%) and Aprostocetus (26.4%). Eurytoma were relatively low at 2.6%. Only about 20% of the immature galls sampled at another site in central Saskatchewan in mid-season had Periclistus and 19.1% by the time the galls matured (Table 5). The mean number of Periclistus per mature gall is also low (Table 4). No parasitoids mature and exit mature galls in the season of gall induction (Table 3).

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