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Chaetosiphon potentillae

Silverweed aphid

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

Identification & Distribution

Adult apterae of Chaetosiphon potentillae (see first picture below) are yellowish or whitish. The head has well developed, angular, antennal tubercles and a large median frontal tubercle. The third antennal segment has 8-12 thick capitate hairs (cf. Chaetosiphon fragaefolii  which can be found on silverweed and has 2-7 thick capitate hairs on that segment). The fourth and fifth antennal segment are usually without secondary rhinaria (cf. Chaetosiphon fragaefolii which has 2-10 secondary rhinaria on the fourth segment and 0-1 on the fifth). The dorsal hairs of apterae are thick and capitate and arise from tubercular bases. Siphunculi are pale, cylindrical, quite thin and with a well developed flange; they are 2.2-3.3 times longer than the cauda which is elongate triangular. The body length of the adult Chaetosiphon potentillae aptera is 1.4-2.1 mm.

The alate (see second picture above) is light green with a central dark patch and several dark transverse bands on the abdominal dorsum. The wing veins are dark brown. The micrographs below show dorsal views of an adult Chaetosiphon potentillae aptera, and an alate.

The clarified slide mounts below are of adult viviparous female Chaetosiphon potentillae : wingless, and winged.

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

Chaetosiphon potentillae does not host alternate, but remains all year on silverweed (Potentilla anserina) and barren strawberry (Potentilla sterilis). Yellowish oviparae and slender-bodied brown apterous males develop in autumn, with overwintering eggs laid on the host leaves.

 

Biology & Ecology

There is a history of confusion in the synonomy and identification of species in the genus Chaetosiphon,  formerly Pentatrichopus (Capitophorus). Thomas & Jacob (1940)  studied both Chaetosiphon potentillae and Chaetosiphon tetrarhodus in his study on the strawberry aphid Chaetosiphon fragaefolii because there was concern that these other species might also be able to live on strawberry. Chaetosiphon potentillae is now known to be confined to Potentilla species and Chaetosiphon tetrarhodus to Rosa species. However, Chaetosiphon fragaefolii is sometimes found on the host of Chaetosiphon potentillae, namely silverweed (Potentilla anserina).

Chaetosiphon potentillae do not form large colonies. They instead live singly or in very small groups.

The adult silverweed aphid (see picture above) moves about the plant depositing her nymphs in ones or twos on the leaves.

After a newborn nymph has been deposited on a leaf (see picture above), it moves to the leaf axil (the crotch between the leaf and stem).

Once there, it flattens itself and hides amongst the long hairs of the host plant (see picture above). This behaviour is described as cryptophilic (= concealment-loving).

In June many of the fourth instar nymphs develop wing buds (see picture below).

They moult to winged alates (see picture below) which disperse to other silverweed plants.

Sexuales develop in autumn, and after mating, the oviparae lay eggs on the leaves of the host plant.

 

Other aphids on same host:

Blackman & Eastop (1984)  list 23 species of aphids that feed on Potentilla anserina and Potentilla sterilis, worldwide.

Of those aphid species, Baker (2015)  lists 18 as occurring in Britain: Acyrthosiphon boreale,  Acyrthosiphon malvae,  Anthracosiphon hertae Aphis craccivora,  Aphis nasturtii,  Aphis roepkei, Aphis tormentillae,  Aulacorthum solani,  Chaetosiphon fragaefolii,  Chaetosiphon potentillae, Longicaudus trirhodus,  Macrosiphum euphorbiae,  Maculolachnus submacula,  Myzaphis rosarum,  Myzus ascalonicus,  Myzus persicae,  Pemphigus ?populi  and Rhopalosiphoninus latysiphon.

Acknowledgements

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

  • Thomas, I. & Jacob, F.H. (1940). The strawberry aphis - Pentatrichopus (Capitophorus) Theob., with notes on P. potentillae Walk. and P. tetrarhodus Walk. Annals of Applied Biology 27(2), 234-247. Abstract