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Aphidinae : Macrosiphini : Pterocomma smithiae
 

 

Pterocomma smithiae

Black willow aphid, Willow grove aphid

On this page: Identification & Distribution Other aphids on the same host

Identification & Distribution

Adult apterae of Pterocomma smithiae (see pictures below) are dark reddish brown, covered with bluish-grey wax powder, and often with a narrow mid-dorsal longitudinal whitish gray line and intersegmental wax lines. There is sometimes a narrow lighter area about the base of each bright orange/yellow siphunculus. Antennal and median frontal tubercles are fairly well developed. The antennal terminal process is 1.0-1.2 times as long as the base of antennal segment VI. The rostrum barely extends to the hind coxae. Abdominal segments II-VII normally each have at least one rounded or bluntly conical marginal tubercle.

First image above, by permission Micki Killoran, all rights reserved;
Second image copyright CBG Photography Group under a Creative Commons Attribution 3.0 License.

The siphunculi are short and stout, about twice as long as their greatest diameter, usually with the maximal swelling near the base (cf. Pterocomma bicolor, which has the siphunculi swollen distally; and cf. Pterocomma populeum, which has the siphunculi almost cylindrical with hardly any swelling). The siphunculi have a well developed flange (cf. Pterocomma salicis, which has a very weakly developed apical flange to the siphunculi). Young immatures (and recently moulted individuals) are salmon pink in color (see second picture below); later they are dark reddish brown with yellow/orange appendages. The body length of adult Pterocomma smithiae apterae is 2.3-4.0 mm.

Note: The siphunculi being swollen on the basal half is usually a good diagnostic character for this species, but some aberrant specimens may have the siphunculi cylindrical or swollen on the apical half (so it pays to examine several specimens!).

First & second images above copyright Sean McCann & Tom Murray respectively under Creative Commons Attribution 3.0 Licenses.
Third image, by permission Micki Killoran, all rights reserved.

The Pterocomma smithiae alate (not pictured) is similarly colored to the aptera. The antennae are a little over half as long as the body, and antennal segment III bears 19-30 secondary rhinaria. There are no dark dorsal abdominal cross bands, but there are marginal and dorsal sclerites which vary from brown spots to large rectangular blotches on each tergite. The siphunculi are vasiform (=vase-shaped).

Pterocomma smithiae occurs on bark of twigs of several poplar (Populus) and willow (Salix) species. The black willow aphid is monoecious holocyclic. Oviparae and alate males occur in October-November. As with most Pterocomma species, it is usually ant-attended (see third picture above). It is common and widely distributed through North America, and in Mexico.

 

Other aphids on the same host

Pterocomma smithiae has been recorded on 7 poplar species (Populus alba, Populus angustifolia, Populus deltoides deltoides, Populus deltoides occidentalis, Populus grandidentata, Populus tremuloides, Populus trichocarpa).

Pterocomma smithiae has been recorded on 3 willow species (Salix alba, Salix fragilis, Salix glauca).

Acknowledgements

We are grateful to Micki Killoran for permission to reproduce his images of Pterocomma smithiae, and to Sean McCann, Tom Murray and CBG Photography Group for making their images available for use under creative commons licences.

We have used the keys and species accounts of Monell (1879) (as Chaitophorus smithiae) and Richards (1967), together with information from Roger Blackman & Victor Eastop in Aphids on Worlds Plants. We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure provided by Blackman & Eastop (2006).

Useful weblinks

References

  • Monell, J. (1879). Notes on Aphidinae, with descriptions of new species. Bulletin United States Geological Survey 5, 18-32.

  • Richards, W.R. (1967). The Pterocomma of Canada and Greenland with notes on the phyletic position of the Pterocommatini (Homoptera: Aphididae). The Canadian Entomologist 99(10), 1015-1040. Abstract