Diastrophus turgidus
Red raspberry knot gall wasp

Host: Red raspberry (Rubus strigosus).

Gall location: On the stem.

Description: Large, multiple-chambered swellings rather similar in appearance to the blackberry knot gall. Generally smooth and fleshy, but usually densely covered with thorns. Unlike the blackberry knot gall, the red raspberry knot gall lacks distinct longitudinal grooves and is instead rather regular in its surface texture. Reddish to greenish and fleshy when fresh to brown and dry when old.

Range: Likely widespread, thus far known along the border of the US and Canada as well as Alaska and some records from Central Canada.

This gall is rather poorly known, as demonstrated by its disparate range. The range and appearance of this gall separate it from the blackberry knot gall.

Diastrophus turgidus

A large reddish-brown polythalamous, tubercular or irregular gall, about 1 to 1.75 in long and .5 in in average diameter, arising abruptly on the stem. Green in summer, darkening towards winter. Chambers are very numerous, oval in shape, 1.5 to 2 in in width and 2.3 in deep. The gall has a number of prickles scattered over it which are about 2 to 3 mm long and appear to be enlarged stem prickles.

Diastrophus turgidus Bassett, 1870

Nomenclature: Diastrophus turdigus [sic] Bassett, 1870

Feeds on: Induces galls on Rubus strigosus Michx.

Distribution: Canada: Manitoba, Newfoundland and Labrador, Ontario, Québec; United States: Colorado, Maine, Minnesota, New York, Ohio, Vermont

Diastrophus turgidus

raspberry
Abrupt stem swelling up to 65 by 30 mm and covered with prickers.

[Photo caption]
On wild raspberry. Adults emerged May 1-June 10 (Chi). Brodie reared the maker May 21-27 Toronto

Diastrophus turdigus, N. Sp.

Looking over my collection of galls, I find a gall from the stalk of Rubus strigosus and several gall insects reared from the same. The gall is an inch long, and three-fourths of an inch thick — an abrupt swelling involving the whole circumference of the stalk. Quite a large number of insects seem to have escaped from it, though many of them were parasites, 1 have only five specimens of the true gall-fly, and these are all females.

Diastrophus turgidus

Rubus strigosus

Mass. Over winters. All around stem.

Diastrophus turgidus Bassett.

Diastrophus turdigus BASSETT
Diastrophus turgidus ASHMEAD
Rhodites radicum RILEY

Gall. (Plate XXVI, Figs. 3, 4, 5, 6, 7, 8, 9; Plate XXVII, Fig. 1). On the stalk of wild red raspberry (Rubus strigosus) and probably allied species. Polythalamous. Abrupt pithy swellings surrounding the stem. Irregular in shape, smooth or more or less covered with short spines. Length 25 to 75 mm.; width 15 to 30 mm.

Habitat: Canada (Ontario); New England States to Massachusetts; Ohio; Colorado.

The adult of D. turgidus somewhat resembles that of D. nebulosus. It differs in having the parapsidal grooves not so widely separated as in nebulosus, and the face less coarsely aciculate. It is also as a rule darker in color. Turgidus is hardly distinct from nebulosus, and may ultimately prove to be the same. The types are in the American Museum of Natural History and American Entomological Society.