Diastrophus potentillae
Cinquefoil bud gall wasp

Host: Dwarf cinquefoil (Potentilla canadensis) and common cinquefoil (P. simplex).

Gall location: On the axil. Description: Single-chambered, globular swellings 8-13 millimeters in diameter. Sometimes with fine hairs. The chamber resides at the center of the gall and is surrounded by fleshy material that becomes spongy as the gall matures. Often with leaf remnants growing out of the outermost layer. Green when fresh to reddish in later stages.

Range: Throughout Northeastern and North-central North Ameica, from Nova Scotia west to Minnesota and south to North Carolina and Tennessee.

This gall is often quite locally abundant, as its two host plants are rather weedy and occur in high density, especially in nutrient-poor environments.

Diastrophus potentillae Bassett, 1864

Nomenclature: Gonaspis potentillae (Bassett, 1864)

Feeds on: Induces galls on Potentilla canadensis L. and P. simplex Michx.

Distribution: United States: Illinois, Indiana, Massachusetts, Maine, Minnesota, NorthCarolina, Ohio; Canada: New Brunswick, Nova Scotia

Gonaspis potentillae

Potentilla canadensis
Axil gall
Globular, 8-13 mm in dia, green in summer, bearing rudiments of leaves, fleshy, spongy when dry, one-celled.

[Photo caption]

327. On Potentilla canadensis. Adults emerged May 15-18 (Chi); July 1 (Me); June 16 (Great Smoky Mts)

Diastrophus scutellaris n. sp.

Gall unknown.

Diastrophus potentillae n. sp.

Galls On Potentilla Canadensis. They are from .3 to .5 of an inch in diameter, and rather longer than thick, growing in the axils of the leaves ; of a soft spongy consistence when dry, and each contains a single cell in shape and size like the nucleus of C. q. globulus, though not, like that, free from the substance in which it is enclosed. They are rather rare here (Conn.), but I saw large numbers of them in the northern part of Berkshire Co., Mass., last summer. The fly came out May 20th from galls of the previous year's growth. It is much like D. nebulosus 0. 8., but Baron Osten Sacken has compared it with this species, and pronounces it distinct.

The genus Gonaspis was established by Ashmead (1897) based on Diastrophus scutellaris Gillette 1891, which was considered a junior synonym (Weld 1952), and listed as a variety of, G potentillae by Weld (1959). Weld's first treatment has become accepted. Therefore, the genus Gonaspis Ashmead 1897 is a new junior synonym of Diastrophus Hartig 1840.

Gonaspis potentillae Bassett

Diastrophus potentillae BASSETT

Gonaspis potentillae var. scutellaris GILLETTE.

Diastrophus scutellaris GILLETTE
Gonaspis scutellaris ASHMEAD

Gall. (Plate XXIX, Figs. 1, 2, 3). On the axils of leaves of Potentilla canadensis. Monothalamous. Spherical or oblong, usually pointed at the base. Green in summer and brown, pithy in winter. Inside it is soft, spongy and contains an oval, hard, larval cell. Diameter 8 to 12 mm.

Habitat: Ontario, Nova Scotia, Canada; New England States; Middle States; Ohio; Illinois. I have bred Gonaspis scutellaris, which is nothing more than a variety of G. potentillae. I have bred scutellaris from galls identical with those of potentillae. The types of potentilla are in the American Museum of Natural History and the American Entomological Society. The type of scutellaris is in the Laboratory of Natural History at Urbana, Illinois.