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Genus Oestlundiella [Calaphidini]Oestlundiella aphids have an elongated body. The body and appendages of adults are covered in a waxy secretion. Antennae are on distinct, but not large, diverging antennal tubercles. Antennae are 6-segmented, somewhat longer than the body, and provided with subcircular or oval secondary rhinaria. The primary rhinarium is small and round. Antennae of oviparae also bear a few secondary rhinaria. The forewing of the alate has the media vein twice branched, and the pterostigmal vein present, not deeply curved. Siphunculi are truncate, constricted in the middle and placed on broad swollen bases (cf. Euceraphis, which has siphunculi much longer than wide, and not placed on swollen bases). The cauda is elongated, cord-shaped and knobbed in spear-like fashion, with constriction near its distal half (cf. Euceraphis, which has a cauda with a near spherical knob). The anal plate is distinctly and broadly, but not deeply, bilobed. Both cauda and anal plate are hairy. There is only one species in the genus Oestlundiella. They feed on undersides of leaves of alder (Alnus spp.), tending to form small aggregations. They are holocyclic, with apterous oviparae and alate males in autumn. Widely distributed in North America (except the south-east). Oestlundiella flava (Woolly-legged alder aphid) North America except South-east USAAll 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) 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. 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 preferred feeding site varies seasonally as the leaf ages and phloem flow changes. 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.
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