Diplolepis nebulosa

Diplolepis nebulosa was first described from unknown localities in the northeastern United States (Bassett 1890). Beutenmüller (1907, 1914) recorded the species from Connecticut, New York City, and Ontario. It is found sporadically across the prairies but sometimes occurs in such large numbers that hundreds can be collected in an hour. Galls are most commonly found on roses growing in the Mixed Grassland Ecoregion of southern Alberta and Saskatchewan.

Galls are spherical, averaging 5.0–7.0 mm in diameter, spineless, and on the abaxial leaf surface (Fig. 22). They occur singly or in a row and sometimes coalesce. Galls are green when immature and light brown when mature. They are single-chambered (Fig. 23) and the walls of mature galls are thin and brittle. Mature galls often abscise before their host leaves do. Periclistus-modified galls are larger and much firmer than inducer-inhabited galls. Galls are initiated in mid-spring.

Beutenmüller (1907) recorded galls on R. blanda and R. carolina L. in eastern North America. On the prairies and in southern British Columbia, these galls are found on R. woodsii. The most common habitat for D. nebulosa is on short R. woodsii, averaging 0.75 m in height and growing on dry, exposed sites. A large population of galls from the flood plain of the Oldman River northwest of Coaldale, Alberta, illustrates a typical community for this species (Fig. 44D). Inducers made up 8.8% of the inhabitants, whereas 32.1% were Periclistus. Parasitoids, mainly Orthopelma and Aprostocetus, formed 59.1% of the inhabitants. A higher percentage (66.6%) of galls were inhabited by Periclistus (average of 3.3 per gall; Table 4) in mid-season, which declined to 13.1% by the time galls were mature (Table 5). For Eurytoma and Torymus, 16.6% and 26.4%, respectively, of individuals exited galls by the fall (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^©