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Brachycaudus malvae

Mallow aphid

On this page: Identification & Distribution  Biology & Ecology 

Identification & Distribution:

Adult apterae of Brachycaudus malvae are pale green with separate black cross bars on thoracic segments, and an extensive shining black sclerotic shield on the dorsum. The hairs on the third antennal segment are very short, only 0.2-0.25 times the basal diameter of that segment. The last two fused apical rostrall segments (RIV + V) are 0.165-0.190 mm in length. The siphunculi are black and cylindrical. The body length of Brachycaudus malvae apterae is 1.8-2.3 mm.

Abdominal tergite 8 bears 10-14 short hairs, not in a single row. Marginal tubercles are often absent; if present they are usually only on the prothorax and abdominal tergites 2-4.

The clarified slide mounts of adult viviparous female Brachycaudus malvae : wingless, and winged are shown below.

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

Brachycaudus malvae is closely related to Brachycaudus cardui  and Brachycaudus lateralis  in the subgenus Acaudus.

Brachycaudus malvae lives all year feeding on mallow (Malva) species with no host alternation. Aphid colonies are usually attended by ants. Sexual morphs have apparently not been described. The species is found in Britain, Spain, Italy, southern Russia, Ukraine and China (an odd distribution suggesting the species has been overlooked in many countries).

 

Biology & Ecology:

There is a real dearth of information about Brachycaudus malvae in the literature. Coeur d'acier (2007)  using molecular techniques notes that Brachycaudus malvae is most closely related to Brachycaudus jacobi, a species which utilizes a quite different host family (Boraginaceae). Jousselin et al. (2010)  uses Brachycaudus malvae as an example of how speciation in the genus has been via the acquisition of new somewhat distantly related hosts (in this case Malva) during the summer phase of the heteroecious (host alternating) life cycle.

In Britain Baker (2009)  found large colonies of Brachycaudus malvae feeding on several common mallow (Malva sylvestris) plants, growing on the edge of a pebble beach at The Knap, Barry, in Wales during summer 2008. Feeding was concentrated on basal parts of the plants where they were sheltered by Lasius niger, but some aphids moved to feed on aerial parts as summer progressed.

We have found Brachycaudus malvae on several occasions in southern England, both in East Sussex and in Bedfordshire. The picture below shows a dense colony on mallow in East Sussex, with a single adult aptera and numerous immatures.

The pictures below show micrographs of a normal apterous adult of Brachycaudus malvae and of an apparently albino example of the same species.

 

Acknowledgements

Our particular thanks to Roger Blackman for images of his clarified slide mounts.

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

  •  Baker, E.A. (2009). Observations of aphids (Aphidoidea) new to Wales. British Journal of Entomology and Natural History 22, 235-246. Abstract 

  •  Jousselin, E. et al. (2010). Evolutionary lability of a complex life cycle in the aphid genus Brachycaudus. BMC Evolutionary Biology 2010, 10: 295. Abstract