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Aphidinae : Macrosiphini : Macrosiphum wilsoni
 

 

Macrosiphum wilsoni

Fairybells aphid

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

Identification & Distribution

Adult apterae of Macrosiphum wilsoni (see picture below) are pale yellowish white, with dusky-tipped siphunculi, and a pale cauda. Antennal segment VI and the tips of tibiae are dusky, and tarsi are dark. Antennal segment III has 1-10 secondary rhinaria, with the longest hair on that segment 0.50-0.86 times the basal width of the segment. The head often has small, low spinal tubercles. The antennal tubercles are medium-sized. The rostrum reaches to the mesocoxae. The apical rostral segment (RIV+V) is 1.0-1.2 times the second hind tarsal segment, and bears 7-11 accessory hairs (cf. Macrosiphum euphorbiae, which has RIV+V 0.8-1.0 times HTII). The abdominal tergum is moderately sclerotic, and somewhat wrinkled. Tergites VII and VIII usually have low spinal tubercles. The siphunculi have a reticulated zone distally (cf. Aulacorthum solani, which has no reticulated zone on the siphunculi). Below the reticulations, the siphunculi are slightly swollen. The siphunculi are 1.0-1.4 times longer than antennal segment III, and 2.3-3.4 times the cauda (cf. Macrosiphum euphorbiae, which has siphunculi 1.7-2.2 times the cauda). The cauda has 7-10 hairs. The body length of adult Macrosiphum wilsoni apterae is 2.2-3.9 mm.

Image above copyright Andrew Jensen under a creative common licence.

Alate Macrosiphum wilsoni viviparae (not pictured) are pale yellowish, with the sclerotized areas distinctly brown. The femora have about the apical half dusky to light brown, and the ends of the tibiae, and all of the tarsi, are brown. Antennal segment III is lightly imbricated, with 13-21 secondary rhinaria scattered over almost entire length, usually with a small gap apically. The longest hair on antennal segment III is 0.53-0.73 times the basal width of that segment. The abdominal tergum has large marginal sclerites on segments II-IV, small marginal sclerites on segments I, and V, large pleural intersegmental muscle attachment plates on segments I-V and sometimes cross bands on some or all of segments I-V. There are also large postsiphuncular sclerites. The siphunculi are dusky to light brown throughout, except the extreme base, which is pale. The cauda is dusky.

Image above copyright Sten Porse under a creative common licence.

Macrosiphum wilsoni is monoecious on fairy bells (Prosartes = Disporum spp.), and has been collected on both Hooker's fairy bells (Prosartes hookeri, see picture above) and largeflower fairy bells (Prosartes smithii). Jensen (2000) notes that both of these plants are perennial, and remain vegetative throughout the summer months. Alatae migrate readily from their home plant upon emergence. Macrosiphum wilsoni has a holocyclic life cycle with oviparae and alate males in October. Jensen found the species often difficult to find in McDonald State Forest, because it was not faithful to particular patches of plants year to year. They are found in north-western USA (Oregon, Idaho, Washington) and Canada (British Columbia).

 

Other aphids on the same host

Macrosiphum wilsoni has been reported on 2 species of fairybells (Prosartes hookeri, Prosartes smithii).

Blackman & Eastop list 3 species of aphid as feeding on fairybells (Prosartes = Disporum spp.) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 2 as occurring in Britain (Show British list).

Acknowledgements

We are grateful to Andrew Jensen and Sten Porse for making their images of Macrosiphum wilsoni and Prosartes hookeri respectively available for use under a creative commons licence.

We have used the species account given by Jensen (2000), 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

  • Jensen, A.S. (2000). Eight new species of Macrosiphum from Western North America, with notes on four other poorly known species. Proceedings of the Entomological Society of Washington 102(2), 427-472. Full text