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Genus Aulacorthum

Aulacorthum aphids

On this page: Genus Aulacorthum  Aulacorthum palustre  Aulacorthum solani 

Genus Aulacorthum [Macrosiphini]

Aulacorthum apterae are medium sized and may be whitish, yellowish, green, pinkish-red or brown, often with a patch of different colour at the base of each siphunculus. The dorsum is sclerotic and shiny. In the genus Neomyzus  (formerly considered a sub-genus) the dorsum has a pigmented pattern. The antennae are usually longer than the body and the head is distinctly spinulose (=has small spines). The antennal tubercles are well developed with near parallel steep-sided inner face (cf. Neomyzus where they are converging). Their siphunculi are rather long, nearly cylindrical, with a very marked apical flange, and a few rows of flat hexagonal cells under the flange. The cauda is rather short and tongue-shaped.

There are 48 species of Aulacorthum aphids, on a great variety of hosts. Most do not host alternate and are monophagous with a sexual stage in their life cycle. A few are highly polyphagous, often with no sexual stage in their life cycles. Some of these polyphagous species are important crop pests. Aulacorthum aphids are not ant attended.

 

Aulacorthum palustre (Wax-banded daisy aphid)

Adult apterae of Aulacorthum palustre are whitish green, pale green or pinkish with black tips to the antennae and legs. The dorsum and antennae have short capitate hairs. They often have rust-coloured or darker green spots around the bases of the siphunculi. The siphunculi are straight and pale, 1.8-2.5 times the length of the cauda, often with conspicuous darkened flanges. Immature Aulacorthum palustre have serial cross bands of whitish wax powder around the body (see pictures below of fourth instar nymphs), but these are apparently lost by the adult stage.

The alate Aulacorthum palustre is reddish or greenish with a brown or black abdominal dorsal pattern. The siphunculi are brown or with brown apices.

Aulacorthum palustre feed on the underside of leaves of plants in the daisy family (Asteraceae) such as cats ear (Hypochaeris), oxtongues (Picris), and possibly dandelions (Taraxacum) and hawkbits (Leontodon). They do not host alternate but live all year round on the same host. They may produce sexuales in autumn and overwinter as eggs, or they may overwinter parthenogenetically as viviparae. Aulacorthum palustre is found throughout Britain and much of Europe.

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Aulacorthum solani (Glasshouse - potato aphid, Foxglove aphid)

Aulacorthum solani apterae are pear shaped and shiny greenish yellow, usually with a bright green or rust coloured patch at the base of each siphunculus. Their antennae have darkened joints and are slightly longer than the body. Their siphunculi are pale with dark tips, long, slender, tapered and distinctly flanged. The body length of Aulacorthum solani apterae is 1.5-3.0 mm.

The winged forms have darker antennae, legs and siphunculi and have a variably developed pattern of tranverse dark bars on the dorsal abdomen.

Unusually for an aphid, Aulacorthum solani can go through the sexual phase on many different plant species - but, in temperate climates, most of their population overwinters as nymphs or apterae, especially on potato sprouts and on many glasshouse plants and wild species such as foxglove (Digitalis). As a result, Aulacorthum solani is often one of the first aphid species to find on young plants in the spring.

Aulacorthum solani is extremely polyphagous, it will colonise plants in may different dicotyledonous and monocotyledonous families. The high toxicity of the saliva of the glasshouse - potato aphid may produce deformation and discoloration of leaves being fed upon. This results in direct feeding damage to potatoes and peppers. Aulacorthum solani can also be a vector of about 40 plant viruses, but its relatively poor virus transmission efficiency makes it unimportant as a virus vector in the field. Its importance is much greater in glasshouses. Its distribution is virtually cosmopolitan.

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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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References

  • Blackman, R.L. & Eastop, V.F. (2006). Aphids on the world's herbaceous plants and shrubs. Vols 1 and 2. John Wiley & Sons.

  • Heie, O.E. (1980-1995). The Aphidoidea, Hemiptera, of Fennoscandia and Denmark. (Fauna Entomologica Scandinavica) E.J. Brill, London.