Besbicus mirabilis Kinsey

Life history

AGAMIC GENERATION. The heterosexual females oviposit during late April to mid-June. Typically, the globular galls containing agamic females appear from mid-May until late August, and normally continue development for about 10 weeks. Galls that appear after mid-July seldom attain maturity. The galls form on the principal veins of the leaf, nearly always on the under surface. Before a gall becomes evident its position on the leaf is marked by the swollen egg-slit in the underside of the vein, and a pale transverse hump on the upper surface of the leaf.

The gall first appears as a tiny fuzzy green swelling that becomes spherical and changes color to a pale yellow. As development progresses the gall becomes smooth, soft yellow or green, finely spotted with reddish brown, and matures into a thin-shelled brownish-yellow globe. The galls are about 0.5 mm. in diameter when first noticeable, and their mature size ranges from approximately 5.0 mm, to 30.0 mm., with the average about 13.0 mln. Many of the galls become misshapen because of insect activities, crowding, or injury. Ordinarilly 1-4 galls may be found on a leaf, but frequently the number is much greater and up to 38 galls have been observed on a single large oak leaf. One small oak tree, 12 inches high, with 65 leaves on its 48 inches of branches, had 72 large galls (Fig. 5). Such concentrations of galls are usually found in low growth next to the ground, where the ovipositing females are afforded greater protection. On Vancouver Island the growth season for the galls is usually over by mid-September, when the oak leaves begin to fall. The galls may be blown from the leaves or fall with them to the ground and become covered with autumn litter. The galls are practically waterproof and their double wall provides excellent insulation for the young insect. The agamic females emerge from these galls from mid-December to early January, and may live as long as 6 weeks. They leave irregular subcircular exit holes in the galls. The adult (Fig. 1) and gall (figs. 3, 5) of agamic B. mirabilis have been adequately redescribed by Kinsey (1929).

There may be considerable variation in the life history pattern because the pupae and ultimate-instar larvae frequently go into diapause for periods varying from a few weeks to several months. The immediate factors influencing the diapause periods have not been ascertained. The diapause is apparently responsible for a 2-year population cycle, augmenting the regular population every other year. During the progress of this study, leaf galls were abundant in even years and relatively scarce in odd years, with the exception of 1962-1963 when there was a moderate population in both years. This cycle apparently has little effect on the numbers of associate insects, most of which-could utilize other hosts.

Besbicus mirabilis

Quercus sadleriana, garryana
Leaf galls
Spotted oak apple, 25–50 mm.in diameter. Usually single on underside of leaf on a vein. Aug., Sept. Fig 92.

Fig 92. Q-garryana and sadleriana. Types are from Portland, Oreg. but galls have been collected in California. Young galls in June become full-grown in August; contain pupae in mid-Sept. and adults in Mid-January. Normal emergence date unknown.

Hosts:
Quercus garryana
Quercus sadleriana

Cynips mirabilis Kinsey

The writer collected galls of this species at Victoria, British Columbia ; on San Juan Island, at Tillicum and Shelton, Wash. ; at Albany, Corvallis, Eugene, Odell, Cottage Grove, Oakland, Canyonville. Wolf Creek, Kirby, Holland, McLeod, and Siskiyou, Oreg. ; at Yreka, Fort Jones, Scott Bar, and Sequoia National Park, Calif. The National Museum has galls from Grants Pass and Goble (E. J. Perkins), Oreg., and O. J. Murie collected galls at Cottage City. The young galls may be found in early July, becoming full-grown in August; they contain pupae in mid-September and the writer cut out living adults from the dry galls on November 10, January 13, and February 14. The forest-insect collection has flies from Ashland, Oreg., which emerged November G and April 1.

Besbicus mirabilis

This cynipid wasp induces large, round, hollow, monothalamous oak-apple galls on the midrib on the underside of leaves of Oregon oak.

Host:
Quercus garryana

Cynips mirabilis, new species

Holcaspis maculipennis
Cynips maculipennis
Amphibolips quercus-inanis (error)

GALL. — Globular leaf gall; monothalamous; 15.-35. mm. in diameter, thin-shelled, smooth, yellowish brown, rather closely marked with irregular, purplish brown spots. Internally with a hard-shelled larval cell, 3. X 5. mm., held centrally by a moderately dense mass of silky, sparingly branched fibers. On leaves of Quercus garryana.

RANGE. — Washington: White Salmon. Oregon: Ashland, Junction City, Grants Pass, Roseburg, Canby; Portland (E. 0. Hovey) ; Albany (Trotter). California: Ukiah(?), Yreka; McConaughy, Siskiyou Co. (Fullaway) ; Elsies Creek, Amador Co. (G. Hansen, in Gray Herb.). Probably found thruout northern California, Oregon, Washing- ton, and British Columbia, wherever Q. garryana occurs.

By a mistake in identification of this Hovey material, this species has gone thru the literature as Gillette's maculipenninis. The two are generically related, but are very distinct species. Maculipennis was described from New Mexico, and is restricted as far as I know to a southern Rocky Mountain area; mirabilis is confined to the Vancouveran zone of the Pacific Coast, at present recorded only from Quercus garryana, or some of its varieties, on which oak it is very abundant. Apparently adults emerge late in the fall or early in the spring, for by early March the galls are all vacated. This species belongs to Cynips Hartig; and not to Cynips of most American authors ; the species shows also some characteristics of Amphibolips, with which genus the physiology reflected by gall characters would connect the insect.

Cynips mirabilis
agamic form

Gall. Large, spherical, spotted, thin-shelled leaf galls with dense, silky, radiating fibers. Up to 33.0 mm., averaging nearer 20.0 mm. in diameter, symmetrical, normally spherical except where drawn out a bit at the attachment; very finely pubescent when young, largely smooth and naked when old, only microscopically shagreened, greenish or with a reddish tinge when young, brownish-yellow or more russet when old, more or less closely set with small, reddish-purple spots. Rather thin-shelled, the larval cell central, supported by numerous, fine, silky, radiating, branched fibers, the cell large, broadly oval, up to 5.0 mm. in length. Attached to the larger veins, singly or near each other, on the under surfaces of leaves of Quercus garryana.

RANGE. — Probably found wherever Q. garryana or any of its forms occur, from British Columbia into northern California and further south along the Sierras. Figure 34. FIG. 34.

[Kinsey goes on to describe 2 varieties of this gall; see paper for details]

Holcaspis maculipennis Gillette

Gall. (Plate IX, Figs. 2, 3.) Single or in clusters of two or more, on the upper and under sides of the leaves of oak (Quercus wrightii [erroneous], Quercus undulata [erroneous], Quercus garryana), and probably other. allied species. Globular, yellowish, composed of a thin outer shell and a single larval cell held in place by radiating fibres. Yellowish brown when dry and covered with darker brown rounded spots. Diameter 15 to 35 mm.

Habitat. New Mexico [erroneous]; California; Oregon. The maculation of the wings is unlike that of any other species of Holcaspis, and the species may be readily known by the continuous parapsidal grooves. The gall resembles that of Amphibolips inanis.

The types are with Prof. C. P. Gillette. I have bred several specimens of the flies from galls collected at Portland, Oregon, by Dr. E. O. Hovey.