Bassettia ligni
Agamic generation

[Photos of this gall appear on page 6 of the pdf]

GALL (Figs. 9-1 1 ). Monothalamous cells beneath the bark, approximately 1 x3 mm (Fig. 10); single, confluent, or crowded. Crowded galls often small and irregular in form (Fig. 11). Oviposition is usually in twigs at least 2 years old, so galls and emergence holes appear on third-year growth (Fig. 9), but they may be present in 2- to 6-year growth. Single or scattered groups of galls are seldom apparent, but when a twig is heavily attacked it is slightly swollen and growth is adversely affected (Fig. 12). After the insects leave, the cells become dark in color and sometimes contain a staining fungus. Emergence holes may remain visible on the branch for several years. Galls may be on trees of any age, and often seem restricted to an individual tree within a group.

Range: northern CA and possibly central OR

Agamic females emerge from the bark in mid-April; individual "colonies" have an average emergence span of only 5 or 6 days. They prefer calm sunny days with temperatures above 55°F to oviposit in the leaves within the swelling buds. The cream-colored eggs are elongate conic-ovoid, ca. 135X.055 mm. Dissected females contained an average of 320 eggs. The galls of the bisexual generation become visible in about 4 weeks.

Bassettia ligni Kinsey

Quercus douglasii, dumosa, durata, garryana, lobata
Stem galls, woody stem swellings or cells under the bark
Fig 60. Scattered cells under the bark.

60. Left to right, two twigs of Q, durata, dumosa, douglasii, lobata. Cells are in two-year-old wood. Types were emerging March 29 (Galt).

Bassettia ligni

On May 20, 1966, an undescribed leaf gall (Fig. 1 a), from which both male and female Cynipidae were emerging, was found on Q. lobata at Locke, Sacramento County. The females readily oviposited in twig growth of the previous year when confined on Q. lobata seedlings in the laboratory. The galls which appeared in the fall of 1966 were those of B. ligni (Fig. 1 b). This species is also known to occur on Q. douglasii Hooker & Arnott and on Q. dumosa Nuttall (Weld 1957a).

Bassetia ligni, new species

GALLS (P1. XXIV, Fig. 1).-Cells within the wood of small twigs, usually not distorting the stem, or producing hardly noticeable swellings. Each cell is elongate-oval, about 1.0 by 2.5 mm., with a shell-like lining, distinct from but hardly separable from the wood; the cells lie wholly within the wood, which is not particularly modified; often a hundred or more are closely crowded in dense clusters. Exit holes, cleanly circular, about 0.5 mm. in diameter, disclose the infestation. On twigs of Quercus Douglasii.

Range: —California: Galt.

This very distinct genus regularly produces galls of about this simple type, and search for exit holes in otherwise undeformed twigs will prob-ably produce, as I have already experienced, more species of the group. Species have been obtained heretofore only from Georgia, Florida, Missouri, Colorado, Arizona, and New Mexico, but not from the Pacific Coast. Insects were still emerging at Galt on March 29, but apparently most of them had emerged previously. The galls were mostly in the two-year-old wood, only rarely in the wood of the previous summer; but whether it takes the species more than one year to develop I cannot say because it was not carefully determined at the time which galls were producing the emerging insects.

Bassettia ligni Kinsey, 1922

Biology--Alternate asexual and sexual generations are known. The asexual generation induces integral leaf galls while the sexual generation stimulates stem galls on Q. douglasii, dumosa, and lobata. The adults of the sexual generation emerge from leaf galls during June to mid-July; the adults of the asexual generation emerge from the bark during mid-April.

Distribution--CA, OR