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Oestlundiella flavaWoolly-legged alder aphidOn this page: Identification & Distribution Other aphids on the same hostIdentification & DistributionAll adult viviparae of Oestlundiella flava are alate. The alatae are lemon yellow covered with plumes of bluish white wax, which are especially long and conspicuous on the antennae and hind legs. The antennae are longer than the body, and are ringed with black at the apices of the segments. Segment III bears subcircular secondary rhinaria. The rostrum reaches to between the first and second pairs of coxae. The prothorax is pale with two parallel longitudinal lateral stripes. The thoracic lobes and scutellum are pale brown, the latter with a black posterior border. The legs are pale or dusky with tips of tibiae, and the entire tarsi, black. Lateral areas of the abdomen are dusky. Body hairs are inconspicuous. The siphunculi are dark brown and truncate with an enlarged distal end, and have a distinctly mammiform base. The cauda is short, pale and globular, and the anal plate has a V-shaped cleft. The body length of adult Oestlundiella flava alatae is 2.4-3.4 mm
Both images above copyright Karen Anthonisen Finch, under a creative commons licence. Immature Oestlundiella flava (see second picture above, and first below) are pale yellow-green, and are not waxed. Fourth instars develop spinal and marginal longitudinal rows of dusky spots, especially on the more anterior abdominal segments.
Images above copyright Karen Anthonisen Finch, under a creative commons licence. Oestlundiella flava lives in rather dispersed colonies on the undersides of the leaves of alder (Alnus species). Blackman indicates that they feed along either side of the mid-rib, although this is not apparent in the colony pictured here, where both alatae and immatures were feeding on the much smaller tertiary and quaternary leaf veins (see first picture above). Perhaps their prefered feeding site varies seasonally as the leaf ages and phloem flow changes. The aphids pictured were sharing their host with the woolly alder aphid (Prociphilus tessellatus, see second picture above) which mainly feeds on the branches and stems of alder. Oestlundiella flava (the woolly-legged alder aphid) is monoecious holocyclic, with sexuales developing in October. It is widely distributed in North America, except in the south-east, but is said to be rather rare. Other aphids on the same hostOestlundiella flava has been recorded on 2 species of alder (Alnus rhombifolia, Alnus rubra).
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