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Aphidinae : Macrosiphini : Macrosiphum olmsteadi
 

 

Macrosiphum olmsteadi

Northern green aster aphid

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

Identification & Distribution

Adult apterae of Macrosiphum olmsteadi (see first picture below) are pale green or brownish-green. The joints of their antennal segments are dusky, and the distal 0.1 of the tibiae and all of the tarsi are dark. The antennal tubercles are produced, diverging, and smooth. The hairs on antennal segments are usually about one-half the basal diameter of the antennal segment. There are 2-7 secondary rhinaria on the basal half of antennal segment III. The rostrum is very hairy reaching to the third pair of coxae. The apical rostral segment (RIV+V) is 0.18-0.19 μm in length, not more than twice its basal width and with 34-45 accessory hairs (cf. Illinoia subviride, which has RIV+V more than twice its basal width and with 14-28 accessory hairs). Tarsal segment I has three hairs. The siphunculi are pale at the base, but progressively darker towards the apices. They are very slightly swollen, usually narrowing at beginning of reticulated area. The cauda is parallel-sided basally, tapers to a blunt point distally, and has 7-9 hairs. The body length of adult Macrosiphum olmsteadi apterae is 2.64-3.01 mm.

Note: Jensen in Aphidtrek notes that Macrosiphum olmsteadi is very close to a species described as Illinoia magna on the same host by Hille Ris Lambers (1974), differing only by having 5, rather than 3, hairs on tarsal segment I. Blackman suggests these species may be synonomyous.

First image above copyright Andrew Jensen, second image copyright Franz Xaver;
both under a creative common licence.

The alate Macrosiphum olmsteadi is green with 12-15 secondary rhinaria in a straight line on antennal segment III. There are irregular dusky transverse bars on the abdominal dorsum, and marginal sclerites usually present on abdominal segments I-IV. The basal two-fifths of the siphunculi are pale, the remainder dusky, except slightly paler at the distal end.

Macrosiphum olmsteadi is monoecious, feeding on eastern showy aster (Eurybia conspicua, see second picture above) and bigleaf aster (Eurybia macrophylla). In Washington Jensen found it common on its host plants in shaded forest and also on the rare flowering specimens, feeding mostly on the undersides of the leaves. It is holocyclic with oviparae and alate males occurring in October. Macrosiphum olmsteadi has so far been found in the northwestern USA (Idaho, Montana, Washington) and Canada (Ontario, British Columbia, Alberta).

 

Other aphids on the same host

Macrosiphum olmsteadi has been recorded on 2 Eurybia species (Eurybia conspicua, Eurybia macrophylla).

  • Blackman & Eastop list only 1 species of aphid as feeding on eastern showy aster (Eurybia conspicua) worldwide, namely Macrosiphum olmsteadi. This species does not occur in Britain.

  • Blackman & Eastop list 2 species of aphid as feeding on bigleaf aster (Eurybia macrophylla) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 0 as occurring in Britain (Show British list).

Acknowledgements

We are grateful to Andrew Jensen and Franz Xaver for making their images of Macrosiphum olmsteadi and Eurybia conspicua respectively, available for use under a creative commons licence.

We have used the species account given by Robinson (1965) together with information from Roger Blackman & Victor Eastop in Aphids on Worlds Plants. We fully acknowledge these authors and those listed in the reference sections 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

  • Hille Ris Lambers, D. (1974). On American aphids, with descriptions of a new genus and some new species (Homoptera, Aphididae). Tijdschrift voor Entomologie 117(4), 103-155. Full text

  • Robinson, A.G. (1965). A new genus, new species and previously undescribed morphs of aphids (Homoptera: Aphididae). The Canadian Entomologist 97, 1009-1015. Abstract