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Large mottled yarrow aphidOn this page: Identification & Distribution Other aphids on the same host
Identification & Distribution:Adult Macrosiphoniella sejuncta apterae are usually green mottled with brownish red, with no wax powdering (see two pictures below). The antennae are rather dark with a paler base to segment III. Macrosiphoniella sejuncta siphunculi are greenish brown to brown with paler bases and the cauda is a pale greenish brown. The body length of the adult aptera is 2.5-3.1 mm.
The first tarsal segment has only 3 hairs. Their siphunculi are very thin, slightly swollen at the base, slightly widened at the apex and with reticulation on the apical 48-69%. The siphunculi are 1.7 to 2.2 times the length of the cauda. The picture below left shows the pale cauda in profile along with some red nymphs of another species, Uroleucon achilleae.
The alate is much like the apterous viviparous female, but is more slender and has well developed marginal sclerites as well as presiphuncular sclerites (see micrograph of clarified slide mount above right). The third antennal segment has 30-40 rhinaria. The ovipara is similar to the apterous vivipara, but the cauda is slightly thicker and blunt, and the basal half of the hind tibia is swollen (see first micrograph of clarified slide mount below).
The male is wingless and small with a body length of only about 2 mm (see second micrograph above).
Macrosiphoniella sejuncta feeds on the older leaves close to the ground of yarrow (Achillea millefolium). The best way to find these aphids is to shake the host-plants over a sheet placed on the soil under the leaves. The species does not host alternate, but remains all year on yarrow - overwintering in the egg stage. Sexual forms can be found in September and October. The large mottled yarrow aphid is found across Europe east to Western Siberia.
Other aphids on same host:
Blackman & Eastop list 46 species of aphid as feeding on yarrow (Achillea millefolium) worldwide, and provide formal identification keys.
Of those aphid species, Baker (2015) lists 26 as occurring in Britain: Aphis craccivora, Aphis fabae, Aphis gossypii, Aphis vandergooti, Aulacorthum solani, Brachycaudus cardui, Brachycaudus helichrysi, Coloradoa achilleae, Macrosiphoniella abrotani, Macrosiphoniella millefolii, Macrosiphoniella ptarmicae, Macrosiphoniella sejuncta, Macrosiphoniella tanacetaria, Macrosiphoniella tapuskae, Macrosiphoniella usquertensis, Macrosiphum euphorbiae, Metopeurum fuscoviride, Microsiphum millefolii, Myzus ascalonicus, Myzus cymbalariae, Myzus ornatus, Myzus persicae, Neomyzus circumflexus, Pleotrichophorus duponti, Trama troglodytes and Uroleucon achilleae.