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Yarrow root aphidOn this page: Identification & Distribution Biology & Ecology: Ant attendance Natural enemies Other aphids on the same host
Identification & Distribution:
Adult Aphis vandergooti apterae (see first picture below) are dark blue-green (or rarely yellow), with blotchy paler areas and no wax powdering. There is usually no dorsal abdominal sclerotic pattern, or there may be narrow bands across tergites 7-8. Marginal tubercles are large and conspicuous but rather flattened (best seen in the micrographs of preserved specimens below). Leg hairs are all very short, much shorter than the least width of tibiae. The siphunculi are tapering, usually widening slightly at the apex with a very small apical flange. The siphunculi are 1.93-2.57 times the length of the cauda. The body length of Aphis vandergooti apterae is 1.4 to 2.0 mm. Immatures are a paler green.
Aphis vandergooti alatae (see second picture above) are dark blue-green and have 3-7 secondary rhinaria on the third antennal segment. The micrographs below show dorsal and ventral views of an aptera in alcohol. The conspicuous, rather flattened, marginal tubercles are clearly shown.
Aphis vandergooti does not host alternate. It lives in ant shelters on the roots, stolons and basal leaf petioles of composite plants of the tribe Anthemideae, especially yarrow (Achillea millefolium), wild chamomile (Matricaria), and tansy (Tanacetum vulgare). Apterous males are produced in autumn. In Britain Aphis vandergooti is widely distributed, but not very much recorded. It is widespread in Europe, but apparently commoner in northern Europe.
Biology & Ecology:
We have found Aphis vandergooti in two counties of southern Britain: in Bedfordshire in a lay-by on the Clifton-Shefford bypass, and several locations in East Sussex including Birling Gap on the coast. They are usually attended by ants, mainly the common black ant (Lasius niger, see picture below).
Woodring et al. (2004) found that Aphis vandergooti takes up much more phloem sap than needed for a minimum of dietary amino acids, and hence can secrete a large volume of melezitose-enriched honeydew. The sole purpose of the sugar-rich honeydew is to solicit the protective services of ants. Those species (e.g. Macrosiphoniella tanacetaria) that do not solicit ants have no need of a sugar-rich honeydew with a high melezitose titre, and only low levels of amino acids and sugars are found in the honeydew.
Depa & Wegierek (2011) looked at the species composition of aphid fauna within the nests of Lasius flavus in three vegetation types: a Molinietum wet meadow, an intensively trodden on and regularly mown Lolio-Polygonetum arenastrii meadow in a housing estate and Festuco-Stipion xerothermic grassland. Aphis vandergooti was only found in nests on the roots of Achillea millefolium and Bellis perennis in the housing estate meadow, which was where the most aphid species rich ant nests were located.
Lysiphlebus fabarum has evolved various adaptations for foraging within ant-tended aphid colonies (Rasekh et al., 2010) and the ants make no attempt to stop the parasitoids from attacking the aphids. In fact foraging Lysiphlebus fabarum females have been observed to remain longer and parasitize more aphids in ant-tended colonies than in unattended colonies (Völkl and Stechmann, 1998). The parasitoids benefit from having the ants protect their developing larvae within the aphids from predators.
On occasions the ants may even antennate the parasitoids in the same way as they antennate the aphids (see picture below where the ant is touching the aphid with one of its antennae).
Possibly this is what Rasekh et al. (2010) termed "recognition antennation" - a behaviour designed to facilitate host recognition.
Other aphids on same host:
Blackman & Eastop list 46 species of aphid as feeding on yarrow (Achillea millefolium) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 26 as occurring in Britain (Show British list).