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Aphis tormentillae

Tormentil aphid

Identification & Distribution  Biology & Ecology 

Identification & Distribution:

Adult apterae of Aphis tormentillae (uppermost aphid in picture below) are rather small and very dark blackish green, appearing black in life. The antennae of the adult aptera often only have five segments. There are small protuberant marginal tubercles on abdominal tergites 1 and 7. Their siphunculi are short and stout, 0.64-1.00 times the length of the cauda. The cauda is finger-shaped and dark like the siphunculi. The body length of the Aphis tormentillae aptera is 1.00-1.67 mm.

 

The dorsal abdominal pattern of Aphis tormentillae aptera is confined to bands across tergites 7-8, small dark intersegmental muscle sclerites and sometimes rudimentary marginal and postsiphuncular sclerites. The alatae have larger marginal and postsiphuncular sclerites with a median sclerite on tergite 6. Immatures are covered with a grey wax powder.

 

Aphis tormentillae lives scattered in small numbers on the leaf bases and in the flowers of tormentil (Potentilla erecta). It does not host alternate. Sexual forms occur in autumn. The males are winged and the oviparae have rather strongly swollen hind tibiae. It is widely distributed in Britain but from very few counties mostly in Scotland. It has only been recorded from one county in England (Sussex) and one in Wales (Merioneth), but there are more records from Scotland. Aphis tormentillae has been recorded from most of Europe and from Russia.

 

Biology & Ecology:

The tormentil aphid may be overlooked, even by experienced aphidologists, because of the small size both of individuals and populations, and lack of ant attendance (Stroyan (1984) ). We have only found it in one location - on the Dundreggan estate in Inverness-shire, Scotland. The host tormentil (Potentilla erecta) was common, and we found Aphis tormentillae on them on three occasions. We found most aphids on the leaf base and on the developing leaves (see picture below).

They are also found on the flowers of Aphis tormentillae, often on the undersides of the bracts (see picture below).

They may even be found inside the flowers, where they remain even after petals have fallen (see picture below).

Colonies were small often with just a scattering of aphids on any one plant. We found no evidence of any attendance of Aphis tormentillae by ants.

References

  •  Stroyan, H.L.G. (1984). Aphids - Pterocommatinae and Aphidinae (Aphidini). Handbooks for the identification of British insects 2 (6). Royal Entomological Society, London.

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).

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