Diastrophus fusiformans
Cinquefoil petiole spindle gall wasp

Host: Slender cinquefoil (Potentilla gracilis).

Gall location: On the leaf petiole, although some accounts state that this gall forms on the stem.

Description: Multiple-chambered swellings ranging from 3-10 centimeters in length. Usually spindle-shaped, but often greatly curved or otherwise deformed. Sometimes with fine hairs. Pithy internally, with chambers suspended in the internal pith. Green to red when fresh to brown when dried and old. Similar to the cinquefoil stem spindle gall wasp (see page 39).

Range: Thus far known from Oregon and Washington, but likely far more widespread throughout the range of slender cinquefoil, at least in Western North America.

This gall, like many others, is realtively poorly known. Interestingly, the slender cinquefoil is quite common and widespread, but this gall is only rarely seen.

Diastrophus fusiformans Ashmead, 1890

Feeds on: Induces galls on Potentilla L. sp.

Distribution: United States: Colorado, Washington

Diastrophus fusiformans Ashm.

Potentilla sp.
Slight fusiform stem swellings, often curved, 35–100 mm. long, cells in the pith. West Cliff, Colorado.

Diastrophus fusiformans Ashmead

Gall. (Plate XXIX, Figs. 15, 16.) On the stems of Potentilla. Polythalamous. An elongate, fusiform swelling, sometimes curved, or otherwise deformed. Length 15 to 45 mm. Diameter 5 to 8 mm.

Habitat: Colorado (West Cliff: T. D. A. Cockerell); Washington (Pullman); Garrison, New York (T. D. A. Cockerell); Massachusetts, Miss Cora H. Clark.

This species is unknown to me and Ashmead's description of the adult is here reproduced. The galls occur on different kinds of Potentilla. Prof. T. D. A. Cockerell collected a gall on this plant at Garrison on the Hudson, New York, which in appearance is the same as D. fusiformans, and Miss Cora H. Clark sent me fusiform swellings on Potentilla canadensis which may also prove to be D. fusiformans when the adults are bred from them. The records New York and Massachusetts, therefore are doubtful. The types are in the United States National Museum.