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Identification & Distribution

Adult apterae of Amphorophora gei are deep yellow to pale green with dusky swollen siphunculi and a thick cauda (see pictures below) (cf. Acyrthosiphon malvae ssp. potha which is yellowish or greyish green, but does not have swollen siphunculi). The antennae are about 1.2 times the body length, with the terminal process of antennal segment 6 about 5.0-7.1 times the length of the base of that segment. Antennal segment III has 1-10 secondary rhinaria with its longest hairs 17-30 μm long. Marginal tubercles are usually absent from the abdomen. The siphunculi are about 2.3-3.1 times the length of the cauda with the swollen apical part nearly twice as thick as the basal part. The cauda is thick, with 7-9 hairs. The adult body length of of Amphorophora gei apterae is 2.2-3.9 mm.

Both images above copyright Alan Watson Featherstone  all rights reserved.

Alate Amphorophora gei have the abdomen green with small marginal sclerites and narrow, not very dark, cross bands on the anterior part. Each antenna has 19-32 secondary rhinaria on segment III in a row over its whole length. The clarified slide mounts below are of adult viviparous female Amphorophora gei : wingless, and winged.

Micrographs of clarified mounts  by permission of Roger Blackman, copyright AWP  all rights reserved.

Amphorophora gei is most commonly found on the undersides of the leaves of water avens (Geum rivale) in moist shady places, although it does also occur on other Geum species. Sexual forms are thought to occur in autumn with overwintering eggs laid on Geum. The water avens aphid is found infrequently in Britain, but is widespread in continental Europe, and has been introduced to the USA.

 

Biology & Ecology

The water avens aphid has only rarely been found in Britain. It was first recorded as alatae on sticky traps in Edinburgh by Doncaster & Broadbent. It was then found on herb bennet (Geum urbanum) in Cambridge, where it occurred in mixed species populations with Myzus persicae,  and Aulacorthum solani,  (Stroyan, 1950 ). The conservationist and photographer Alan Watson Featherstone found the aphid recently (2018) on water avens (Geum rivale) at Glen Affric in the Highland region of Scotland, and has contributed the photos for this page.

Image above copyright Alan Watson Featherstone  all rights reserved.

Water avens grows in bogs and damp meadows and produces nodding brownish-purple flowers. Amphorophora gei may be found feeding on the underside of the leaves, and on the stems and flowers.

Both images above copyright Alan Watson Featherstone  all rights reserved.

The swollen siphunculi and thick cauda (see pictures above) are distinctive characteristics which (at least in Europe) are not shared with any other species found on Geum. Amphorophora gei is known to overwinter on Geum because fundatrices have been found in spring, but as yet no sexual forms have been described.

Image above copyright Alan Watson Featherstone  all rights reserved.

Ripka (2011)  recorded Amphorophora gei in Mesteri, Hungary for the first time in 2011.

 

Other species on the same host

Blackman & Eastop list 7 species of aphid  as feeding on water avens (Geum rivale) worldwide, and provide formal identification keys.

Of those aphid species, Baker (2015)  lists 6 as occurring in Britain: Acyrthosiphon malvae ssp. potha, Amphorophora gei, Aulacorthum solani,  Macrosiphum gei,  Myzus ascalonicus  and Myzus ornatus. 

 

Damage and control

Wilkaniec & Piekarska-Boniecka (2008)  observed a damaging infestation of Amphorophora gei on ornamental dwarf orange avens (Geum coccineum) in Poland in 2002.

Acknowledgements

We are very grateful to Alan Watson Featherstone  for his photos of this aphid from Glen Affric in Scotland.

We have made provisional identifications from high resolution photos of living specimens, along with host plant identity. In the great majority of cases, identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and species accounts of Blackman & Eastop (1994)  and Blackman & Eastop (2006)  supplemented with Blackman (1974) , Stroyan (1977) , Stroyan (1984) , Blackman & Eastop (1984) , Heie (1980-1995) , Dixon & Thieme (2007)  and Blackman (2010) . We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in identification or 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

  • Ripka, G. (2011). Redescription of Phylloxerina populi (del Guercio) (Hemiptera: Phylloxeroidea) with notes on other aphids in Hungary. Folia Entomologica Hungarica 72, 17-30. Full text 

  • Stroyan, H.L.G. (1950). Recent additions to the British aphid fauna. Part I. Dactynotus Rafinesque to Rhopalosiphum Koch, C.L. Transactions of the Royal Entomological Society of London 101, 89-124. Abstract 

  • Wilkaniec, B. & Piekarska-Boniecka, H. (2008). Aphid infestation of decorative perennials. Acta Sci. Pol., Hortorum Cultus 7(1), 13-19. Full text