Diastrophus bassettii
Dewberry crown gall wasp

Host: Common dewberry (Rubus flagellaris) and swamp dewberry (R. hispidus).

Gall location: On the crown, at the interface of the stem and root, either above or below the soil line. In rare occasions, this gall can be found further up on the stem and may be mistaken for the similar galls, especially if the host plant is not identified to species.

Description: Multiple-chambered, globular swelling. Sometimes nearly spherical, but usually appearing as an amorphous botryoidal cluster of kernel-like chambers. Greenish to reddish when fresh. Highly variable in size, usually 1-3 centimeters in diameter but occasionally larger.

Range: Historically, this gall has been found throughout the Northeastern United States, but some records suggest it occurs as far south as North Carolina.

This gall was rather poorly known until the recent past. They are often locally abundant, and can often be found by locating a single gall and following the stems to find additional galls, even on the same plant.

Diastrophus bassettii Beutenmüller, 1892

Feeds on: Induces galls on Rubus procumbens Muhl. and R. hispidus L.

Distribution: United States: Connecticut, Massachussets, North Carolina, New Jersey,New York, Rhode Island

Diastrophus bassettii

Blackberry
Irregularly globose, half-buried in the ground at tip of running blackberry or dewberry. Adults emergin July 7.

[Photo caption]

321. On running blackberry.

Diastrophus bassetti Beutenmuller

Gall. (Plate XXVIII, Figs. 1, 2, 3, 4, 5). On the stems at the roots, or partly below the surface of the ground, on trailing blackberry (Rubus canadensis) and probably allied species. Polythalamous. Irregularly rounded or somewhat elongated or almost globular in shape. Composed of a fleshy substance when fresh and pithy when dry and mature. Greenish or yellowish green, tinged with red or sometimes almost entirely red. Diameter from 12 to about 25 mm.

Habitat. New York; New Jersey; Connecticut; Massachusetts; Rhode Island; North Carolina (Black Mts.).

The adult may be known from its congeners by the strong aciculations and the fine linear elevation on the face, the aciculations on the mesothorax, and dark rufous legs and antennae. It is allied to D. radicum. The gall is sometimes quite common locally, reaching maturity late in autumn. The types are in the American Museum of Natural History and American Entomological Society.