Weldia plumbella, new combination
Disholcaspis plumbella
Adleria plumbella
Gall: Monothalamous bud or stem galls occurring singly or in clusters on young stems; stem galls bear an elongated groove at the point of attachment (an indentation made by the stem); bud galls bear a circular indentation at point of attachment (which corresponds to the shape of the bud base); most galls spherical, some with an apical projection 1 to 3 mm long, sharply pointed, others without such a projection; surface usually smooth, bare.
Internal structure: Larval capsule spherical, centrally positioned in gall, composed of two layers, inner nutritive and outer protective layer; nutritive layer indistinct or absent in mature galls, outer layer thin; capsule surrounded by parenchymal tissue composed of elongate, woody columnar cells radiating away from point of attachment; flattened collenchymal zone positioned just below epidermis composed of compressed cuboidal cells; epidermins composed of small crystalline cells compressed into a thin lyaer 1 or 2 cells deep, forms hardened surface. Color: Growing galls pale green with whitish spots when in constant shade, shades of brilliant red or wine with yellow spots when constantly exposed to direct sunlight; mature galls light brown with pale yellow spots which are occassionally embossed, distributed uniformly over gall surface. Size: Average of 100 unparasitized galls: horizontal diameter, 10.6 mm, length of apical projection, 1.9 mm (galls without apical projections not included in the latter measurement).
Galls of W plumbella vary considerably in size and in some populations 80% of galls lack the apical projection. Galls on Q turbinella californica [john-tuckeri] at desert margins are typically small (9 mm or less in diameter) with only an apical nipple or short, thin projection. Galls on Q dumosa, from Monterey Co northward, bear a long, stout apical projection to 3 mm or more in length.
Hosts: Quercus dumosa, durata, and turbinella californica [john-tuckeri]
Range: CA and northern Baja California
Gall Growth. New galls appeared on Q dumosa at Site No 2 [near San Bernardino] on 2 May 1974, and on Q t californica [john-tuckeri] at Site No. 1 [also near San Bernardino] ca mid-June. Small galls growing from within bud scales and later on new stems were pale green with reddish patches when exposed to the sun. At this time, many galls possessed a blunt apical projection. Galls which failed to exhibit this character were round and smooth apically at maturity. By 1 August, most galls at Site No 2 were approximately 5 mm in diameter and distinctly pointed apically with an orange-red background color and bright yellow spots. Galls growing on lower branches and shaded from direct sunlight were various shades of green with white or yellow spots. On 1 October, galls were full-sized (ca 10.5 mm in diameter), round, moist internally, and still vividly colored. By 10 November, they had weathered to a light tan and the yellow spots were either absent or subdued.
The internal structure of the mature galls is similar to that described for galls of W californica, however, the cells of the parenchyma are smaller and less elongate in W plumbella and the larval capsule is round and centered in the gall. In galls of W californica, the larval capsule is oval and subcentral.
Old galls rarely are numerous on branches, as their attachment to stems is fragile and they are easily knocked to the ground by wind and rain. Frequently after a storm, 60-80% of the galls in an area (even those from which adults have not yet emerged) may be found lying on the ground, where they fall prey to birds and rodents which crack them open, apparently to eat the contained insects.
Galls arise from either terminal or axillary buds on the previous year's branch or from a new branch of the current year's growth. As with galls of W californica, W plumbella stem galls result when eggs in buds hatch after new stems have begun to grow. This causes the newly emerged first instar larva and its surrounding gall tissue to be carried with the stem as it grows. The mature stem gall may ultimatley rest several centimeters beyond the original site of oviposition. Bud galls result when eclosion occurs prior to incipient stem growth. Mature bud galls may be recognized by the presence of scales clinging to the gall base.
Rearing Adults. Mature galls were collected from Q dumosa [berberidifolia?] near Site No 2 in September and October, 1974, and kept outdoors as rearing stock for oviposition experiments. Normal emergence of parthenogenetic females began on 7 October and continued until 21 November.
[Burnett goes on to describe findings of dissections and oviposition experiments.
[From key to galls, page 176 of the pdf]
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Spherical or cone-shaped stem galls, usually with an apical projection or strong surface tubercles
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Surface smooth; pointed apically
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Surface of mature galls brown or reddish with yellow spots (uniform light brown when weathered), smooth, usually with pointed apical projection; larval capsule central, spherical, thin-walled; on Q dumosa, durata, Q turbinella californica [john-tuckeri] and hybrids.
