Diplolepis fusiformans (Ashmead)

Diplolepis fusiformans was first described from galls found in Colorado (Ashmead 1890). They have also been found in Ontario, Illinois, Nebraska, and Arizona (Beutenmüller 1907; Kinsey 1922; Burks 1979; Caouette and Price 1989). Diplolepis fusiformans is one of the smallest wasps in the genus, with females averaging 1.5–2.5 mm in length.

Galls of D. fusiformans are small, fusiform, and found along the terminal parts of the current-year stems (Fig. 32) of R. woodsii. Galls may be a gentle swelling or may be swollen to about twice the size of the host stem (Fig. 32). Galled stems are smooth and often have a split in the epidermis. The gall is multi-chambered with a series of chambers, usually about five in a row, along the length of the stems (Fig. 33). Galls are internally woody, soft, and porous and the chambers are inseparable. Chambers containing Periclistus are also found along the lengths of the stem (Fig. 33).

Adults of D. fusiformans exit their galls in late June and oviposit in new sucker shoots about 5 cm in length. In contrast to all other species of Diplolepis, D. fusiformans deposits its eggs on the exposed surface of the stems (Shorthouse et al. 2005). The galls form after the larvae enter the stem.

Galls are found throughout the grasslands of the prairie provinces and southern British Columbia on R. woodsii. They have not been reported on R. arkansana or R. acicularis. In Ontario, D. fusiformans forms galls on R. blanda but not on R. acicularis. No data on the component communities associated with this gall were obtained.

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