Diplolepis bassetti (Beutenmüller)

Diplolepis bassetti was first described from galls collected near Corvallis, Oregon (Beutenmüller 1918). However, the gall illustrated by Beutenmüller is that of the European multi-chambered gall of D. rosae, whereas galls of D. bassetti are single-chambered. Because D. rosae is established in Oregon, this early report likely confused the two species. Kinsey (1922) provided a detailed description of the adults and recognized two subspecies. However, he also appears to have confused the galls of D. bassetti and D. rosae.

Diplolepis bassetti induces mossy, monothalamous galls (Figs. 28 and 29) on the adaxial surface of the leaflets of R. woodsii in open habitats in southern Alberta and Saskatchewan and in the Okanagan Valley of British Columbia. Diplolepis bassetti is also sparsely distributed across southern Alberta and southwestern Saskatchewan.

Galls are usually found in dense clusters. Their surface is covered with soft filamentous hairs (Fig. 29) that are green to red when immature, turning brown when mature. Galls are initiated in mid-summer. The chambers rarely coalesce and the individual galls can be easily separated. Galls average 4–5 mm in diameter. They commonly remain attached to the host plant throughout the winter.

Two large populations of mature galls collected in the spring were chosen to illustrate community composition. One collection was made on the flood plain of the Oldman River north of Coaldale at the same site as the D. ignota galls (Fig. 44E). The second was made from several large patches of roses from Kelowna to Osoyoos, British Columbia. No data were obtained on the seasonal changes of Periclistus attack, the number of Periclistus per modified gall, or the percentage of parasitoids exiting galls in the fall.

Inducers were by far the most abundant inhabitants (Fig. 44I) at the southern Alberta site. Galls here also had few Periclistus, representing 2.8% of the community. Only 19.6% of the remaining inhabitants were parasitoids, with the most abundant being Pteromalus (7.8%) and G. stigma (7.5%). In contrast, galls from southern British Columbia (Fig. 44J) had fewer inducers (16%) and Periclistus were much more abundant (28.4%). Parasitoids constituted 55.3% of the emergents, with the most abundant being Aprostocetus (46.9%) and Eurytoma (5.5%).

Diplolepis bassetti subsp. bassetti (Beutenmüller, 1918)

Nomenclature: Rhodites bassetti Beutenmüller, 1918

Feeds on: Induces galls on Rosa nutkana C. Presl and R. woodsii Lindl.

Distribution: United States: Oregon; Canada: Alberta, British Columbia,Saskatchewan

Diplolepis bassetti subsp. lucida Kinsey, 1922

Nomenclature: Diplolepis bassetti var. lucida Kinsey, 1922

Feeds on: Induces galls on Rosa nutkana C. Presl

Distribution: United States: Idaho, Oregon

Diplolepis bassetti (Beut.) 1918 Canad. Ent 50: 307 [bisexual] Corvallis, OR.

Produces an abrupt, mossy, terminal mass, 17-30 mm in dia, strongly concave at point of attachment. On Rosa nutkana. Adults in late Feb to March.

Rosa nutkana
Stem swellings
Woody, covered with green filaments, 17-39 mm in dia, terminal on twigs of Rosa nutkana. Type from Oregon.

[Photo caption (Weld reproduces Beutenmuller's drawing Figure 14)]
Beutenmuller's original figure on Rosa nutkana. Terminal, green when fresh, 17-38 mm in dia. Types from Corvallis OR. Galls collected in December gave adults (indoors) in late February and early March. Galls were seen at Waitsburg, WA.

Rhodites bassetti, sp. nov.

Gall. — (Plate IX, Figs. 13, 14). On the tips of the twigs of Rosa nutkana. Polythalamous. A rounded, hard and woody gall densely covered with long, green filaments forming a moss-like mass as in Rhodites rosae, and strongly concave at the place of attachment. Diameter 17-38 mm.

Habitat. — Corvallis, Oregon. (B. G. Thompson). A number of galls of this species were sent to me by Mr. B. G. Thompson, collected December 10th, 1916. At first I considered them to be Rhodites rosae Linn. But when the flies began to emerge (indoors) during the latter part of February until about the middle of March, I found that they were different from R. rosae in sculpture and colour. The gall, although similar externally to R. rosae, differs by being more woody inside and strongly concave at the place of attachment, being almost like an inverted cup or bowl in shape, while the gall of R. roses, is composed of an agglomeration of hard cells around a branch. Named after the late Homer F. Bassett.

Diplolepis bassetti

This wasp induces large round, detachable, polythalamous stem galls on Nootka rose, pine rose, and interior rose, among other species and hybrids. The galls look like balls of moss or hair.

Hosts:
Rosa nutkana ssp nutkana
Rosa pinetorum
Rosa woodsii ssp ultramontana

Diplolepis bassetti (Beutenmuller)

GALL. — Mossy, containing a compact or agglomerated cluster of woody cells. Filamentous covering 4.0-8.0 mm. thick, probably green and reddish when young, becoming brown and blackened with age; filaments attached to a more or less compacted cluster of larval cells, each cell sub-spherical, 2.0-4.0 mm. in diameter, with woody but not thick walls, entirely hollow within. On the twigs, usually terminally, of Rosa nutkana.

RANGE. — Oregon, Idaho, and Utah. Probably elsewhere in the northwest.

Morphologically the insects of this species are decidedly related to Diplolepis rosae, and less closely to D. bicolor. Significantly, the galls of variety bassetti show striking similarity to those of rosae. The galls of the other variety, tho superficially similar to rosae, are in all respects merely a compact cluster of galls of the D. bicolor type, differing mainly in possessing the filamentous covering. The evolutionary transition from the galls bicolor to rosae, or the reverse procedure, cannot have been more profound than the evolution of the two types of galls in this one species.

There will be no question that this is a single species, for the characters separating the two varieties are very few. But if one has any doubt of the validity of the varieties he should examine a large series of individuals, when he should be impressed with the constancy of the distinctions within these few characters. Geographic isolation has probably contributed materially to the separation of two forms, for as far as the ranges of the two are known at present they are separated by the high altitudes of the barren lava-bed country of western Oregon. The type localities of the two are two hundred and fifty miles apart. Moreover, variety bassetti occurs in a region of excessive precipitation and tempered seasons, while the other variety occurs in the very arid deserts of the northern Rocky Mountains, a country of extreme climate. I should not consider this a variety of Diplolepis rosae, tho the two are very close. Rosae seems to be a native of Europe, but has more or less of a world-wide distribution, being readily imported into new regions; and apparently the species reached the eastern part of the United States as an importation from Europe. Rosae has not been recorded from west of the Rockies. No species native to America is very closely related to rose except this Pacific Coast species, bassetti. There may be considerable significance in this situation.

Diplolepis bassetti variety bassetti (Beutenmuller)

Rhodites bassetti Beutenmuller, 1918, Can. Ent., L, p. 307, pi. IX, figs. 13, 14.

GALL. — Superficially resembles the gall of the other variety, but is distinct as follows: Filaments finer, more dense and curled; often a hundred or more larval cells in a cluster, the cells thoroly fused together, forming a perfectly solid, woody mass; galls averaging large, often up to. 45. mm. in diameter.

RANGE. — Oregon: Corvallis (Beutenmuller) ; Ashland.

Beutenmuller states that galls collected in December gave adults from late February to the middle of March, indoors. Most of the adults had not yet emerged from the galls collected at Ashland on April 6.

Diplolepis bassetti variety lucida, new variety

GALL. — Superficially resembles the gall of the other variety, but is distinct as follows: Filaments heavier, broader, straighter; usually only 30 or fewer larval cells in a cluster, each cell more or less entirely separate, with a proximate origin from the stem, the cells compacted into an insecure mass more by the intertwining filaments than by a fusion of the wood of each cell; the whole mass averaging smaller than in the other variety, 25. mm. the maximum diameter noted.

RANGE. — Oregon: La Grande. Idaho: Mountain Home.

Few of the adults had emerged on April 12 at La Grande, and on April 20 at Mountain Home Of 267 adults, 100 are males.

The collection at Mountain Home, Idaho, has peculiar interest because that locality is in the heart of the Snake River desert. This is an alkaline, dust desert, barren of most vegetation except sage brush, with an excessively low precipitation ; because of its elevation of about 3500 feet, and its great, level sweep, the region is exposed to severe storms and extreme temperatures in winter, and to a surprisingly hot summer. Repeated searchings at several localities across this desert failed to disclose any plant which might bear Cynipidae. The oaks, mainly eastern species, planted as wind breaks in the towns, failed to disclose galls. Some distance outside of the town of Mountain Home, a few roses were growing beside an irrigation ditch, and there were two galls of this species and variety. I do not know whether the roses were native species or escapes from cultivation ; they bore a native cynipid. How far it may have been to the next colony of roses it would be hard to determine; I am inclined to believe it might have been a considerable distance. Insects and galls of this mate- rial agree in minute detail with material from La Grande, two hundred miles away, mostly across the desert. The desert does possess a system of streams, but roses are few at most along these streams, for I failed to find them at any of a half dozen other points at which I tried to collect.

I collected galls of this type at Brigham, Utah, but did not obtain insects, so I cannot say whether yet another variety will be found for this species.