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Reddish brown willow bark aphidOn this page: Identification & Distribution Other aphids on the same host
Identification & Distribution
Adult apterae of Pterocomma bicolor (see two pictures below) are reddish brown to dusky greenish yellow, greyish or bluish green, with yellow-orange siphunculi. The antennal and median frontal tubercles are fairly well developed. There are no secondary rhinaria on antennal segment III (cf. Pterocomma populifoliae, which usually has up to 25 secondary rhinaria on that segment). Marginal tubercles are present, and are well developed on the prothorax and most of abdominal tergites I-VII. They are variably shaped, but often conical, broad-based, and much larger than the adjacent hair-bases. The dark conical marginal tubercles are visible on the reddish brown specimen in the second image below. The siphunculi have an apical flange, with the apical swollen section sometimes approaching twice the basal diameter (cf. Pterocomma smithiae, which usually has the siphunculi swollen on the basal half, and cf. Pterocomma populeum, which has the siphunculi almost cylindrical with hardly any swelling). The siphunculi have no obvious imbrications (cf. Pterocomma populifoliae, which has dispersed imbrication in addition to normal subapical striae on its siphunculi). The cauda and anal plate are rounded. The body length of Pterocomma bicolor adult apterae is 3.2-4.8 mm.
Note: Jensen suggests that the first image shown below may be of a fundatrix.
Alatae of Pterocomma bicolor (see picture below) have a reddish brown to dusky green abdomen with variably-developed dark brown to black dorsal markings, only sometimes forming complete cross-bands. There are 12-26 secondary rhinaria on antennal segment III, but none on other segments (cf. Pterocomma populifoliae, which has 35-50 secondary rhinaria on III and 0-7 on segment IV). Their siphunculi vary from cylindrical, to distinctly swollen to about 1.5 times the basal diameter on the apical half.
Pterocomma bicolor are monoecious holocyclic on native poplars such as balsam poplar (Populus balsamifera) and quaking aspen (Populus tremuloides). This appears to be by far the most common Pterocomma species in western North America. They are also common on naturalised Salix species such as white willow (Salix alba) and weeping willow (Salix babylonica). They feed on the bark of twigs and small branches, or stems of saplings, or rarely just below the soil surface. Sexual forms (oviparae and alate males) occur in October-November. See Jensen in aphidtrek for an interesting (but brief) discussion on the probable migration of alatae in spring from warmer lowlands to upland areas. Pterocomma bicolor is widespread in North America, from Canada through the USA and into Mexico.
Other aphids on the same host
Pterocomma bicolor has been recorded on 3 poplar species (Populus balsamifera, Populus nigra, Populus tremuloides). Blackman also gives Populus angustifolia as a host in the text, but does not include it in his host list for this species.
Pterocomma bicolor has been recorded on 3 willow species (Salix alba, Salix babylonica, Salix lutea).