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Aphidinae : Macrosiphini : Macrosiphum oregonense
 

 

Macrosiphum oregonense

Western skunk-cabbage aphid

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

Identification & Distribution

Adult apterae of Macrosiphum oregonense (see two pictures below) are shiny yellow-green to green. The body and antennae are generally pale, but their antennae and tibiae are dark-tipped, the tarsi are dark, and the siphunculi are dark or dusky over their apical 0.17-0.20. The antennal terminal process is about 4.7 times the base of antennal segment VI. There are 1-4 secondary rhinaria, which are restricted to the base of antennal segment III, and the longest hair on that segment is 0.65-1.19 times the segment's basal width (cf. Aulacorthum solani, which has the longest hair on that segment 0.2-0.4 times the basal diameter). The antennal tubercles are large, slightly diverging, and the median frontal tubercle is small but distinct. The rostrum reaches to the mesocoxae, with the apical rostral segment 0.85-1.09 times as long as the second hind tarsal segment. The prothorax is usually without marginal tubercles. The abdominal tergum is only faintly sclerotized, sometimes lightly wrinkled, with marginal tubercles usually lacking. The siphunculi have 5-10 rows of reticulations apically, the part just proximal of these often slightly swollen; they are 1.13-1.45 times antennal segment III (cf. Aulacorthum solani, which has siphunculi shorter than antennal segment III). The cauda has 7-11 hairs. The body length of adult apterae is 2.34-3.74 mm. Immature Macrosiphum oregonense are paler green due to a light dusting of white wax.

First image above copyright Alex Bairstow, second image copyright Andrew Jensen,
both under a creative common licence.

Alatae of Macrosiphum oregonense (not pictured) are green with the sclerotized areas brownish, the siphunculi almost entirely brown, and the cauda at most slightly dusky. Antennal segment III bears a single row of 7-17 secondary rhinaria scattered over almost the entire length of the segment, with a short gap apically. Abdominal segments II-IV have large, dark brown lateral sclerites, with various small sclerites on most tergites, and large dark postsiphuncular sclerites, which are fused with a broad cross band on tergite VII.

Image above copyright Martin Bravenboer, under a creative common licence.

Macrosiphum oregonense is monoecious holocyclic on its host, western skunk cabbage (Lysichiton americanum, see picture above). This plant is a semi-aquatic herb with long, broad leaves, often growing in seeps, roadside ditches, and seasonally-flooded areas in Western North America. These aphids feed on the undersurface of their leaves or among the bases of the leaves near the ground. Jensen found that aphids were present on the plant even when it was completely submerged during the winter, and speculated whether this provided an overwintering site for the aphid. Macrosiphum oregonense occurs in western Canada (British Columbia), and the USA (Washington, Oregon).

 

Other aphids on the same host

Macrosiphum oregonense has only been recorded on 1 skunk cabbage species (Lysichiton americanus).

Acknowledgements

We are grateful to Alex Bairstow & Andrew Jensen respectively for making their images of Macrosiphum oregonense available for use under a creative commons licence; also to Martin Bravenboer for putting his image of Lysichiton americanus (Western Skunk Cabbage) in the public domain.

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