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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 first picture below). The antennae are rather dark, but with a very short pale section at the base of segment III. Crescent-shaped antesiphuncular sclerites are well developed (cf. Macrosiphoniella tapuskae, which has barely visible presiphuncular sclerites). Body hairs are thin and long and placed on small scleroites (cf. Macrosiphoniella tapuskae, which has body hairs not placed on distinct scleroites). The first tarsal segment has only 3 hairs. Macrosiphoniella sejuncta siphunculi are greenish brown to brown with paler bases and the cauda is a pale greenish brown. The siphunculi are very thin, slightly swollen at the base, slightly widened at the apex, have reticulation on the apical 48-69%, and are 1.7 to 2.2 times as long as the cauda (cf. Macrosiphoniella millefolii, which has siphunculi 0.8-0.9 times as long as the cauda). The body length of the adult Macrosiphoniella sejuncta aptera is 2.5-3.1 mm.
The Macrosiphoniella sejuncta alate is much like the apterous viviparous female, but is more slender and has well developed marginal sclerites as well as presiphuncular sclerites (see second picture above). The third antennal segment has 30-40 rhinaria. The ovipara is similar to the apterous vivipara, but its cauda is slightly thicker and blunt, and the basal half of the hind tibia is swollen. The male is wingless and small with a body length of only about 2 mm.
The micrograph below shows an aptera viewed dorsally in alcohol - the small hair-bearing scleroites on the dorsum are clearly visible.
The clarified slide mounts below are of adult viviparous female Macrosiphoniella sejuncta : wingless, and winged.
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:
Macrosiphoniella sejuncta has been recorded from 2 Achillea species (Achillea millefolium, Achillea ptarmica).
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).