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Aphis parietariae

Pellitory-of-the-wall aphid

On this page: Identification & Distribution  Biology & Ecology 

Identification & Distribution:

Aphis parietariae apterae range in colour from dark to light green, with pale yellowish summer dwarf apterae. The antennal tubercles are weakly developed. The apterae have bands across tergites 7-8 in larger specimens but the dorsum is otherwise unpigmented. The siphunculi are blackish, much darker than any other sclerotic part of the body. They are 1.0-1.5 times the length of the cauda, which bears 6-10 hairs. The body length of Aphis parietariae apterae is 0.9-1.7 mm.

Aphis parietariae alates have marginal and postsiphuncular sclerites, and a median sclerite on tergite 6 in addition to the bands on tergites 7 and 8 that are present on apterae. The antennae of alates have 4-8 secondary rhinaria on the third segment, 0-2 on the fourth, and none on the fifth.

The pellitory-of-the-wall aphid does not host alternate. It lives in dense colonies on stems, under leaves and on inflorescences of Parietaria species. Sexual forms occur in autumn - the males are apterous. Aphis parietariae is found across Europe, as well as in north Africa and the Middle East.

 

Biology & Ecology:

We have found active Aphis parietariae colonies as early as March in the south of England. The dense colonies that develop later in the year often smother the plants, which become discoloured by sooty mould especially if there are no attending ants. However colonies are usually attended by ants, especially Lasius species, as can be seen in the picture below.

Despite the ant attendance, there may be extensive predation by the 'wax-protected' predator (Scymnus) shown below. Pacheco (2012)  has shown experimentally that the wax on Scymnus larvae reduces intraguild predation by lacewing larvae (Chrysoperla) and presumably by ants.

Outbreaks of aphid fungal disease are also common in large colonies, and may greatly reduce numbers.

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

  •  Pacheco, P.A.B. (2012). Costs and benefits of the morphological defenses in larvae of Scymnus nubilus Mulsant (Coleoptera: Coccinellidae). MSc Thesis, Ponta Delgada, Universidade dos Acores Full text