Diastrophus cuscutaeformis
Blackberry seed gall wasp

Host: Various brambles (see remarks below).

Gall location: On the main stem.

Description: Distinctive, but often quite diverse in appearance. Typically present as large, long clusters of closely-placed, seed-like, single-chambered galls. Green when fresh to red or brown when mature. The size and shape of the individual galls is quite variable, although they usually each have fine hairy filaments, distinct spines, or blunt projections. Individual galls are less than a half centimeter in diameter. Clusters may contain only a few galls, or as many as 100!

Range: Widespread in Eastern North America, from New England and Lower Canada south to Georgia and west to Minnesota and Louisiana. This gall is one of the more common bramble galls, and it is common in many habitat types.

There is currently little consnsus on the true host plant range for this species, as the literature has been inconsistent in its mentioning and treatment of host identifications, but overall, this gall appears to be found on brambles of the subgenus Rubus, specifically species that stand erect. The authors of this guide have thus far found blackberry seed galls on Allegheny blackberry (Rubus allegheniensis) and common blackberry (R. canadensis). Host plants used by this gall can be difficult to identify, but luckily, this gall is rather distinctive.

Diastrophus cuscutaeformis Osten Sacken, 1863

Feeds on: Induces galls on Rubus L. spp.

Distribution: United States: Illinois, Indiana, Massachusetts, Maryland, Maine, Michigan, Minnesota, Missouri, North Carolina, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, South Carolina, Tennessee, Virginia, Vermont; Canada: Newfoundland and Labrador, Ontario

Diastrophus cuscutaeformis n. sp.

Rubus sp. Blackberry. A number of smallround., hollow bodies., forming a cluster round a branch.

I possess two specimens of this gall, collected near Bladensburgh, Md., and kindly communicated to me by Mr. Hitz. The globular, seedlike bodies, each having about 0.1 in diameter and producing a single insect, are (in one of my galls) from 60 to 70 in number, and occupy a space of about an inch and a half on the branch. They are pressed closely together and offer some resemblance to the seeds of Cuscuta, when found in winter attached to a stem. Many of the round bodies emit more or less strong spines, which impair in a measure the regularity of their form. The consistency of their shell is woody; their color brownish, like that of the branch. I was unable to ascertain on what species of Rubus this gall occurs. Besides the Diastrophus., originating this gall, I have obtained from it an Ormyrus and an Aulax., which, as far as I can judge frum a single specimen, is my A. sylvestris., also reared from the other blackberry- gall.

Diastrophus cuscutaeformis

On Blackberry
Cluster of seed-like bodies closely set about the stem for several inches, on weaker canes near the ground.

[Photo caption]
On wild blackberry. Adults out in May (Chi)

Diastrophus cuscutaeformis Osten Sacken

Gonaspis cuscutaeformis

Gall. (Plate XXVIII, Figs. 7, 8, 9, 10). On stalk of blackberry (Rubus villosus, R. canadensis and R. cuneifolium). Monothalamous. Consists of numerous small, globular, woody, seed-like bodies, pressed closely together, each provided more or less with spines or filament. Dark green, turning red as the season advances.

Habitat: Canada (Ontario); New England and Middle States; probably southward to Florida; Illinois; Ohio; Michigan; Iowa; Missouri; Indiana.

The gall is sometimes quite common locally and several hundred are often on a single stalk. It may be readily known by the seed-like bodies, each containing a single larva. Dalla Torre and Kieffer erroneously refer D. cuscuteformis to the genus Gonaspis of Ashmead. The types are in the Museum of Comparative Zo6logy, Cambridge, Mass.